Genetics Study Guide

Why did Mendel use Pea Plants?
1. They grow quickly
2. Came in many varieties
3. ability to self-pollinate
Explain Mendel’s experiment with the 3 generations:
First, he produced true-breeding strains of pea plants. He did this by allowing them to self-fertilize. Next, Mendel crossed the two different varieties in the P1 generation. Finally, Mendel allowed the F1 generation plants to self-fertilize. He called the offspring produced the second filial, or F2 generation.
has two different alleles for a trait
ex: Tt Hh Rr
heterozygous
2 alleles for a trait are the same
ex: TT HH RR
Homozygous
the expressed form of the trait (the trait that is visible); represented by capital letters
Dominant
the trait that is not expressed when the dominant form of the trait is present; represented by lower case letters
recessive
are used to visualize all the possible combinations of alleles from the parents.
Punnett Squares
What do the letters represent?
alleles
For each inherited trait an individual has __ copies of the gene- one from each _________
2, parent
are different gene forms (different versions)
alleles
each allele can be passed on when the___________________
individual reproduces
What did Mendel describe the trait that was being expressed described as?
dominant
what did mendel describe the trait that was not expressed?
recessive
cross between individuals that have different alleles for the same gene
Dihybrid cross
the gene combination an organism contains
genotype
the way an organism looks. the physical expression of a trait
phenotype
Mendel’s ideas were often referred to as…?
the laws of heredity
-the first law of heredity describes the behavior of chromosomes during meiosis when homologous chromosomes and then chromatids are separated
-states that the two alleles for a trait separate when gametes are formed
law of segregation
states that the alleles of different genes separate independently of one another during gamete formation
law of independent assortment
the alleles for a plant height separate independently of the alleles for flower color. This is an example of…? and why does this happen?
Example of Law of Independent Assortment. Because we know that this law applies only to genes that are located of different chromosomes or that are far apart on the same chromosome
it appears in both sexes equally, it does not involve sex chromosomes
autosomal trait
what are the 22 pairs of matching homologous chromosomes called?
autosome
_____is a chromosome other than X or Y chromosomes.
autosome
traits controlled by genes located on sex chromosomes
sex-linked traits
the chromosomes that control the inheritance of sex characteristics are indicated by the letters
X and Y
if you are female, ___________, your 23rd pair of chromosomes look alike
XX
if you are a male, _________, your 23rd pair of chromosomes looks different
XY
If a trait is sex linked, it is usually seen only in…?
males
most sex-linked traits are… dominant or recessive?
recessive
________is an individual that has one copy of the recessive allele but does not have the disease
carrier
a trait controlled by 2 or more genes, occurs when many genes interact to produce a single trait
Polygenic Inheritance
eye color, height, weight, and skin color are examples of…
polygenic traits
the phenotype of a heterozygote is a mixture between those of the two homozygotes (appearing halfway between the two parents) , its a mix between the phenotype of the two parents, neither allele of the pair is completely dominant but comine and display a new trait
incomplete dominance
why do you use all capital letters when doing incomplete dominant problems?
to show that it is different from the traditional genetic cross
the equal expression of both alleles ~ both traits are displayed
Codominance
what is it called when both alleles are expressed equally?
codominance
when a gene has 3 or more alleles for a trait
multiple alleles
a capital i “I” is used to show?
multiple alleles
how are human blood types determined?
by the presence or absence of certain molecules on the surfaces of red blood cells
When IA and IB are both present in the genotype, they are considered…?
codominant (equal expression)
bloody type A’s genotype:
Homo- IAIA
Hetero- IAi
type B’s genotype:
homo- IBIB
hetero- IBi
type AB’s genotype:
IAIB
type O’s genotype:
ii
who was the father of genetics?
gregor mendel
what types of characteristics did mendel choose to study?
plant height, seed shape, flower color
means that it contains both female and male reproductive organs
self-pollination
occurs when you remove the anther from a self-pollinating plant and replace it with pollen form another plant
cross-pollination
is the branch of biology that studies heredity
genetics
is the passing of characteristics from parents to offspring
heredity
are the characteristics that are inherited
traits