Heredity concepts

Meiosis content included with the cell cycle flashcards. /// Not included but good to know: basics of Mendel's pea experiment, simple probability rules, different chromosomal disorders

Where two copies of a gene come from

One each from biological mother and father

Principle of Dominance

Some alleles are dominant and will always show, and some are recessive and will only show when the dominant allele is absent

Mendel’s Law of Segregation

Two alleles separate during meiosis and only one is passed down, with each having an equal chance of doing so

Why Punnett squares can create accurate predictions

Equal segregation of alleles

Purpose of a test cross

To determine the genotype of the dominant phenotype parent

Mendel’s Law of Independent Assortment

Genes don’t influence each other in the sorting of alleles into gametes, and genes for different traits are passed down separately

Incomplete dominance example

In some flower species, the breeding of a red flower with a white one will result in pink offspring

Codominance example

Someone heterozygous for sickle-cell anemia will have both round and sickle-shaped blood cells

Multiple alleles examples

Blood type, rabbit fur color

Sex-linked traits examples

Red-green colorblindness, hemophilia

Why recessive sex-linked disorders are more common in males

They only have to inherit one recessive allele to be affected, whereas females have to inherit two

Indicators of a dominant disorder on a pedigree

Both parents have it, but child doesn’t; present in every generation

Indicators of a recessive disorder on a pedigree

Neither parent has it, but child does; skips one or more generations

Epistasis examples

Labrador coat color, mice fur color

Polygenic trait examples

Skin color, eye color, height

How linked genes can be inherited separately

Crossing over breaks the linkage

Expected ratio of linked genotypes in gametes

1:1 of parental types

Recombination frequency of genes on separate chromosomes

50%

Chances of different gamete types for genes very far apart on the same chromosome

50% parental, 50% recombinant

How distance affects de-linkage

Genes that are closer together are less likely to be unlinked during crossing over

0% recombination frequency meaning

Linked genes with no crossing over

50% recombination frequency meaning

Genes on different chromosomes

0-50% recombination frequency meaning

Genes are on the same chromosome and crossing over occurs some of the time

Why map units do not necessarily equal recombination frequency

Double crossovers

Gamete results after nondisjunction in meiosis I

n+1, n+1, n-1, n-1

Gamete results after nondisjunction in meiosis II

n+1, n-1, n, n

X inactivation example

Coat color is located on the X chromosome in tortoiseshell cats, which have some cells that produce one color and other cells that produce another

Environmental impact on phenotype examples

Human height, weight, and skin color; hydrangea color; reptile sex

How mitochondrial and chloroplast inheritance works

Mitochondria and chloroplasts DNA are passed down by the egg, so if the mother has the trait, all the offspring will, and if she doesn’t, none of the offspring will.