Genetics and Heredity Studyguide – Chapter 11 Biology

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How is your sex determined?
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Your sex is determined by whether you get an X or a Y chromosome from your father. Everyone receives an X from their mother.
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Who is Gregor Mendel?
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Gregor Mendel was an Austrian monk who did genetic experiments in pea plants. He was well educated in biology, math, and physics and taught biology at the monastery.
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What is genetics?
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Genetics is the study of heredity.
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What did Gregor Mendel use to test his theories on heredity?
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Mendel used ordinary garden peas that he was in charge of tending at the monastery.
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Do plants have a sex?
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No, plants have both male and female reproductive parts.
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What does the male part of each pea flower do?
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Each of the male parts of a pea flower produce pollen which contain sperm.
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What does the female part of each pea flower do?
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Each of the female parts of a pea flower produce egg cells (ova).
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What is fertilization?
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Fertilization is the process that takes place during sexual reproduction. The egg and sperm cells join and new life is created.
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Can pea plants self-pollinate?
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Yes, pea plants can self-pollinate.
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What is true-breeding?
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True-breeding is when self-pollinating plants would produce identical offspring to themselves (=homozygous).
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Did Mendel control the breeding?
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Yes, Mendel controlled the breeding very strategically and methodically.
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What is cross-pollination?
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Cross-pollination is where you take the pollen from one plant and using it to fertilize another’s eggs.
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What is a trait?
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A trait is a specific characteristic that varies from one individual to another.
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What are the names for each generation?
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P – parents F1 – offspring (filial) F2 – grandchildren (offspring of F1 generation)
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What is a hybrid?
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A hybrid is the offspring of crosses between parents with different traits are called hybrids (=heterozygous)
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What did Mendel figure out with the F1 generation?
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All the hybrid offspring in the F1 generation had the characteristics of one parent.
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What is did Mendel conclude about how traits are passed?
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Mendel figured out that biological inheritance os determined by factors (=genes) that are passed from one generation to the next.
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What are factors?
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Factors are genes.
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What are alleles?
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Alleles are the different forms of a gene.
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What is Mendel’s principal of dominance?
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Mendel’s principal of dominance states that some alleles are dominant and others are recessive.
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What happens when an organism is dominant for a trait?
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An organism with a dominant allele for a trait will always exhibit that form of the trait.
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What happens when an organism is recessive for a trait?
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An organism with the recessive allele for a trait, the dominant allele will show unless there are multiple recessive alleles.
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What happened when Mendel crosses his F1 generation offspring with themselves?
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The traits controlled by recessive alleles reappeared in 1/4 of the F2 generation offspring.
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What are gametes?
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Gametes are sperm and egg cells.
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What is inside sperm and egg cells?
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Inside sperm and egg cells are alleles.
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What is segregation?
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The separation of alleles during gamete formation.
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What is a genotype?
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A genotype shows what alleles are present (Hh, JJ, ff).
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What is a phenotype?
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A phenotype is what the individual looks like (blue eyes, brown hair, long lashes).
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What is heterozygous?
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Heterozygous is alleles that are different (Gg).
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What is homozygous?
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Homozygous is alleles that are the same (mm, TT).
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What is independent assortment?
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The genes for a specific trait can segregate independently during gamete formation. This means that one set of alleles does not affect another (eye color doesn’t effect hair color).
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What is incomplete dominance?
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Incomplete dominance is when one allele is not completely dominant over another allele (red flower + white flower = pink flower).
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How do you write incomplete dominance alleles?
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The formula for the alleles of incomplete dominance is: a capital letter that you feel classifies the trait/gene followed by a superscript that shows the version of the gene/trait.
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What is codominance?
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Codominance is when the phenotype produced by both alleles are clearly expressed. Usually both alleles are equally represented (speckled, dotted, mixed). For example, a dog that is black and white.
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What are multiple alleles?
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Genes that are controlled by more than two alleles are said to have multiple alleles.
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Can you have more than two alleles?
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No, you cannot have more or less than two alleles. However, more than two possible alleles can exist in a population. One example of this is eye color; you can have brown, blue, hazel, black, violet, gray, or green eyes but you only have two alleles for your eye color.
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What are polygenic traits?
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Traits controlled by two or more genes are said to be polygenic traits. Polygenic traits often show a wide range of phenotypes (skin color).
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What is meiosis?
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Meiosis is the process of how sex cells are formed.
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How many divisions take place in meiosis?
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Meiosis involves two divisions, meiosis I (most important) and meiosis II. The end result is four haploid cells.
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What occurs during interphase I?
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In interphase I, the cells undergo DNA replications and form duplicate chromosomes.
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What happens during prophase I?
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In prophase I, each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
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How many chromosomes are in a tetrad?
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There are four chromosomes in a tetrad.
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What happens during crossing over?
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Chromosomes exchange portions of their chromatids. This produces new combinations of alleles.
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What happens during metaphase I?
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Spindle fibers attach to the chromosomes. The tetrads line up in the center of the cell by the centromeres.
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What occurs during anaphase I?
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The spindle fibers pull the homologous chromosomes toward the opposite ends of the cell. The sister chromatids stay together.
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What takes place during telophase I and cytokinesis?
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Nuclear membranes form and the cell separates into two cells. The two cells produced by meiosis I have chromosomes and alleles that are different from each other.
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What happens during meiosis II?
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The sister chromatids are separated.
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What occurs during metaphases II?
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The chromosomes line up in the center of the cell.
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What takes place during anaphase II?
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The sister chromatids separate and move toward opposite ends of the cell.
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What happens during telophase II and cytokinesis?
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Meiosis II results in four haploid (N) daughter cells.
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What happens in the gamete formation process in males?
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In males, meiosis results in four equal sized gametes called sperm. This takes place in the testes.
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What happens in the gamete formation process in females?
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In females, only one egg results from meiosis. The other three cells, called polar bodies, are usually not involved in reproduction. This takes place in the ovaries.
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Why are polar bodies not typically viable?
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A female produced four cells, but one usually gets most of the nutrients and \”good stuff\” while the other three get very little to none. The three resulting polar bodies are not usually able to survive the four or so days needed to be fertilized and become stable enough to implant in the uterine lining to get nutrients.
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What is a karyotype?
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A karyotype is the visual of the pairs of chromosomes (46, XX) (23, Y).
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How many chromosomes do humans have?
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Humans have 46 chromosomes per cell.
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How many sex chromosomes do human have?
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Humans have 2 sex chromosomes out of the total 46 per cell.
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What do sex chromosomes do?
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Sex chromosomes determine an individual’s sex/gender.
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What are the 44 non-sex chromosomes called?
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The remaining 44 out of the 46 human chromosomes are called autosomal chromosomes or autosomes.
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Which pairs of chromosomes are autosomes?
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Pairs 1-22 are autosomal chromosomes.
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What pairs of chromosomes are sex chromosomes?
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Only pair 23 is sex chromosomes.
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How many X chromosomes do human eggs carry?
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Human eggs carry one X chromosome.
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How many Y chromosomes do human eggs carry?
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Human eggs do not carry a Y chromosome.
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How many X chromosomes do sperm cells carry?
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Half of all sperm cells carry an X chromosome (23,X).
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How many Y chromosomes do sperm cells carry?
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Half of all sperm cells carry a Y chromosome (23,Y).
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What is the average ratio of males to females?
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50:50 due to the way the sex chromosomes segregate during meiosis.
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What is nondisjunction?
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Nondisjunction (most common error in meiosis) occurs when homologous chromosomes fail to separate during meiosis. If nondisjunction occurs, abnormal numbers of chromosomes may find their way into gametes and a disorder of chromosome number may result.
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What is down syndrome?
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Down syndrome occurs if two copies of an autosomal chromosome fail to separate during meiosis. If this occurs, an individual may be born with three copies of the 21st chromosome (47, XX). This causes mild to severe mental retardation and increased susceptibility to diseases and birth defects.
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What is Turner’s syndrome?
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In females, nondisjunction can lead to Turner’s syndrome (45, X). This means the individual has only one X chromosome. Girls with Turner’s syndrome be short, have a webbed neck, heart problems, be sterile, and may suffer from mild mental retardation.
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What is Klinefelter’s syndrome?
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In males, nondisjunction may cause Klinefelter’s syndrome (47, XXY). This means the individual has an extra copy of the X chromosome but still developed as a male. Boys with Klinefelter’s syndrome have feminized body shapes (hips and slight breasts) and are sterile.

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