AP Bio Unit 5 - Heredity

What is a diploid?

a pair of chromosomes

eg. humans have 23 pairs (diploid) but 46 individual chromosomes in total

What happens to the number of chromosomes during meiosis?

it reduces the number by half (to become haploid)

After interphase in meiosis, how does the number of chromosomes change?

it is technically the same number of chromoSOMES, but each chromosome now has its own sister chromoTID

What is a homologous pair?

chromosomes that go in the same spot, with one of the two being from mom and the other being from dad

they code for the same thing, but have different variaiton

eg. eyes, hair, height —→ mom’s one is blue, blonde, short

During what part of the cell cycle does crossing over occur?

prophase 1

What is crossing over?

The homologous pair lines up and swaps bits of itself so that the end product is two chromosomes with parts of each other mixed in

How many sperm are produced from meiosis? How many eggs?

• 4 sperm

• 1 egg

What 3 things allow for genetic diversity from meiosis?

• crossing over during prophase 1

• chromosomes randomly being assorted to each side of the cell, no matter if its your mothers or father genetic information

• random fertilization between sperm and egg

What are Mendelian genetics?

when one gene codes for one characteristic, no funny attached business

Gene v. Allele

gene = area of chromosome for characteristic (eg. eye color)

allele = version of characteristic (eg. blue)

What is the phenotypic ratio of a dihybrid cross (meaning AaBb x AaBb or heterozygous x heterozygous)

9 dominant, dominant : 3 dominant, recessive : 3 recessive, dominant : 1 recessive, recessive

If a gene is dominant, is it always more common?

No, not at all

What are the non-Mendelian patterns?

• Incomplete dominance - the heterozygous is a mix (eg. red x white = pink) also, neither characteristic is dominant)

• Co-dominance - you see both characteristics at the same time (eg. red x white = red and white spotted flowers)

What is the idea of Multiple Alleles?

Any person can only carry two alleles at a time for one gene, but more than two alleles/variants for the gene exist

What is epistasis?

when one gene affects the expression of another gene

What is polygenic inheritance?

multiple genes affecting a single trait

(eg. multiple genes code for skin color, so there are many different types of skin color, not just 2-4)

If genotypes produced aren’t in an even ratio, but are mostly just two of the four possibilities, what is the most likely cause?

(eg. not 24:26:23:27 but 48:2:45:5)

the genes are close together on the chromosomes, meaning that it is less likely for them to be independently assorted during CROSSING over