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Flashcards in Lecture 5 Deck (14):
0

How long is the DNA in a human haploid genome?

1m

1

How is the DNA condensed in the nucleus of human cells?

It is wrapped in nucleosomes which is DNA wrapped around histone octamers. There are 147 base pairs wrapped around one octamer.

2

What is epigenetics?

The study of heritable changes on gene activity that are not caused by changed in the DNA sequence usually by changing the length of the histone tails which can be modified to make chromatin more/less relaxed.

3

What are the 5 stages of prophase?

Leptotene
Zygotene
Pachytene
Diplotene
Diakenesis

4

Describe what happens in the leptotene stage

The chromosomes start to condense

5

Describe what happens in the zygotene stage of prophase

Homologous chromosomes become closely associated (synapsis) to form pairs of chromosomes (bivalents) consisting of four chromatids (tetrads)

6

What are bivalents

Pairs of chromosomes

7

What are tetrads?

4 chromatids

8

Describe the pachytene stage of prophase I

Crossing over between homologous chromosomes to form chiasmata

9

Describe the diplotene stage of prophase i

Homologous chromosomes start to seperate but remain attached by chiasmata

10

Describe the diakenesis stage of prophase i

Homologous chromosomes continue to separate and the chiasmata move to the ends of the chromosomes

11

What are the products of meiosis in human females?

One mature egg cell and 3 polar bodies

12

What are the products of meiosis in human males?

4 identical sperm

13

What is non-disjunction meiosis?

The chromosomes fail to separate properly in either meiosis I or meiosis II