Chromosomes, Genomes, Cell Replication

Question 1

Define Genome and what does it include

Answer 1

The genome is the entire DNA component of a species
Including: introns, genes, intergene reigons and DNA in organelles

Question 2

Viral Genomes

Answer 2

-either DNA or RNA
-linear or circular
-extensive packaging needed to fit the virus

Question 3

Viruses (bacteriophages)

Answer 3

-96% of phages are tailed allowing binding to cell surface and injection of genome into host cell

Question 4

Organisation of DNA in bacteria

Answer 4

-located within the bacterial nucleoid, very little protein associated with genome

Question 5

Nonchromosomal Genetic Material in Bacteria

Answer 5

-plasmids generally beneficial, extracellular
-viruses can be harmful to the cell, often extracellular

Question 6

How do typical plasmids and what are the specialised functions

Answer 6

-replicate independently of chromosome
-‘functions’ antibiotic resistance, metabolism of ‘complex’ sugars, resistance to toxins, conjugation etc.

Question 7

Eukaryotic Chromosomes

Answer 7

-more complex than prokaryotes
-much larger amounts of DNA
-each chromosome contains a single linear double-stranded DNA molecule
-many protein interactions occur
-DNA bound to histones referred to as chromatin
-chromatin fibres condense to form visible chromosomes during cell division (if stained)

Question 8

Steps for Organisation of DNA in Eukaryotes

Answer 8

1- Simplest level, chromatin is a double-stranded helical structure of DNA
2-DNA complexed with histones to form nucleosomes
3-Each nucleosome consists of eight histone protiens around which the DNA wraps 1.65 times
4- Nucleosomes fold up to produce a 30nm fiber that forms loops averaging 300 nm in length
5-The 300-nm fibers are compressed and folded to produce 250 nm wide fiber
6-Tight coiling of the 250-nm fiber produces the chromatid of a chromosome.

Question 9

What occurs during Cell Proliferation?

Answer 9

DNA in chromosome is replicated and chromosomes condense into structures that are visible by light microscopy.

Question 10

Sister Chromatids

Answer 10

Identical chromosomes, joined at their centromeres by kinetrochore

Question 11

Kinetochore

Answer 11

Becomes the anchor point for microtubles that will pull the chromatids apart into the two new cells

Question 12

karyotype

Answer 12

the chromosome complement of a cell arranged by size and shape

Question 13

haploid number (n)

Answer 13

the number of chromosome pairs in a somatic cell

Question 14

haploid cell

Answer 14

a cell e.g gamete with one set of chromosomes

Question 15

diploid number (2n)

Answer 15

the total number of chromosomes in a somatic cell

Question 16

diploid cell

Answer 16

a somatic cell with two sets of chromosomes

Question 17

sex chromosomes

Answer 17

those chromosomes determining sec (humans X and Y)

Question 18

autosomes

Answer 18

all non-sex chromosomes

Question 19

standard karyotype in humans

Answer 19

23 pairs of homologous chromosomes
23rd pair determines the sex
xy=male
xx=female