Chromosomes and Cell Division Flashcards Preview

Principles of Disease > Chromosomes and Cell Division > Flashcards

Flashcards in Chromosomes and Cell Division Deck (23):
1

What is the end replication problem?

through multiple generations, strands will get shorter

2

What is the solution to the end replication problem?

telomerase

3

What are centromeres?

-Protein complexes that bind to microtubules and are required during cell division
-They are the constricted region joining sister chromatids
-site of kinetochores
-repetitive SNA sequences- satellite DNA

4

Hererochromatin vs Euchromatin

-Heterochromatins has a condensed structure and silenced genes
-Euchromatin has an open structure and active genes

5

Describe the structure of chromatin.

-formed of DNA packaged histones
-histones have a positive charge, DNA negative
-146 bp DNA wrapped around core of 8 histones= nucleosome
-further wrapping of nucleosomes
-form solenoid structure

6

By what factor is DNA condensed by at metaphase?

10,000

7

What is the purpose of packaging DNA?

-negatively charged DNA neutralised by positive charged histone proteins
-DNA takes up less space
-Inactive DNA can be folded into inaccessible locations until required

8

What is colchine?

-a microtubule inhibitor
-it enriches the population of cells that are visible

9

Metacentric

p length= q length

10

Submetacentric

p length< q length

11

acrocentric

p length <<< q length

12

What does FISH stand for?

Fluorescent in situ hybridisation

13

What types of FISH probes are there?

-unique sequence probes
-centromeric probes (useful for determining chromosome number)
-telomeric probes (detecting subtelomeric rearrangements, often present in children wit unexplained mental retardation)
-whole chromosome probes (cocktail of probes, used with different dyes, spectral karyotype, detecting translocation and rearrangements)

14

What is meiosis?

-cell division in germ cells
-diploid cells (in ovaries and testes) divide to form haploid cells)
-chromosomes are passed on as re-arranged (recombinant) copies which creates genetic diversity

15

What is a defining event in sexual reproduction?

recombination between homologues

16

What are the 2 forms of gametogenesis?

-oogenesis= process of egg formation
-spermatogenesis= process of sperm formation

17

Why is there a greater chance of mutation in sperm than in eggs?

they go through more cell divisions

18

How many sperm and eggs are produced in each cycle of gametogenesis?

-4 sperm
-1 egg + 3 polar bodies

19

Describe fertilisation.

-two haploid cells form 1 diploid cell which develops into an embryo
-whether sperm contains an X or Y chromosome determines if the embryo is female or male
-embryo contains an assortment of genes from each original parent- more genetic diversity

20

What is maternal inheritance?

mitochondria (and their DNA) come only from the mother via the egg

21

When does X inactivation occur?

-In the zygote both X chromosomes are active
-In the early embryo random inactivation of one X occurs

22

What are 2 tandemly repeated DNA extragenic sequences?

-satellite DNA
-microsatellite DNA

23

What are 2 highly repeated interspersed DNA extragenic sequences?

-SINEs (short interspersed nuclear elements)
LINEs (long interspersed nuclear elements)