AP Bio Later Units

Locus

the position of a gene on a chromosome

P generation

parent generation

F generation

filial generation

Dihybrid cross of two heterozygotes for two genes

9 dominant for both

6 dominant for one, not other

1 that is recessive in both

Product Rule

If A and B are independent, the P ( A and B ) = P(A) times P(B)

Sum Rule

If A and B are mutually exclusive, then P (A or B) = P(A) + P(B)

Barr body

The X chromosome that is condensed and visible, that is active

Incomplete dominance

traits blend, neither is dominant over the other

Codominance

Equal expression of both alleles

Polygenic inheritance

trait results from the interactions of many genes

Non-nuclear inheritance

mitochondria and chloroplasts from the egg

In a pedigree, how to tell if a trait is sex linked

If it appears more in one than the other

In a pedigree, how to tell if a trait is recessive

It skips generations

Phenotypic plasticity

Two individuals with the same genotype have different phenotypes because they are in different environments

Meiosis I Prophase I

• Nuclear membrane disappears, the centrioles move to opposite sides of the nucleus

• The chromosomes line up with their homologs

• Crossing over occurs, when segments are exchanged between homologous chromosomes

Synapsis

• The chromosomes line up with their homologs during Prophase I of Meiosis I

• The two sets of chromosomes come over to form a tetrad

• Crossing over occurs, when segments are exchanged between homologous chromosomes

Meiosis I Metaphase I

The chromosome pairs (tetrads) line up at the metaphase plate and the alignment is random

Meiosis I Anaphase I

Each pair of chromatids within the tetrad moves to the opposite poles

Meiosis I Telophase I

• Nuclear membrane reforms around each set of chromosomes

Meiosis II

Similar to mitosis, to separate the sister chromatids

Nondisjunction

chromosomes fail to separate properly during meiosis which means that there is aneuploidy or the incorrect number of chromosomes in a cell

Aneuploidy

aneuploidy or the incorrect number of chromosomes in a cell

Translocation

When a segment of a chromosome moves over to a nonhomologous chromosome