3 Chromosomes, Meiosis, and Linkage Free Online FlashCards

What is chromatin?

Chromatin is DNA packaged with proteins, especially histones.

What are sister chromatids?

Sister chromatids are the two identical DNA molecules produced when a chromosome is copied; they remain joined until they separate.

What is the centromere?

The centromere is the region where sister chromatids are joined.

What distinguishes homologous chromosomes from identical copies?

Homologous chromosomes carry the same genes at corresponding loci, but can have different alleles. One homolog is inherited from each parent.

What is a gene locus?

A locus is the specific position a gene occupies on a chromosome.

What separates during meiosis I?

Meiosis I separates homologous chromosomes, reducing the chromosome number by half; sister chromatids remain joined.

What separates during meiosis II?

Meiosis II separates sister chromatids, which move to opposite poles.

What is independent assortment?

Independent assortment is the independent orientation of chromosome pairs during meiosis I. For $n$ pairs, it can produce up to $2^n$ combinations of whole chromosomes.

What is crossing over?

Crossing over is the exchange of corresponding DNA segments between nonsister chromatids of paired homologs during prophase I.

How does chromosome linkage affect gene inheritance?

Linked genes are on the same chromosome and tend to be inherited together; recombination can separate them.

How is recombination frequency calculated?

Recombination frequency is the percentage of offspring that are recombinant: $\frac{\text{recombinant offspring}}{\text{total offspring}}\times 100\%$.

What does a recombination frequency of $1\%$ represent for nearby loci?

For nearby loci, $1\%$ recombination is approximately $1$ map unit, or $1$ centimorgan $cM$.