molrcular bio of the gene 3

Question 1

what are chromosomes?

Answer 1

Chromosomes are all the genes and intergenic DNA that code for proteins and make up genetic sequence

Question 2

what are the components of chromosomes

Answer 2

o Genes are genetic info that codes for proteins and RNA
o Intergenic DNA are regulatory sequences for gene transcription, inheritance and packaging of genes

Question 3

how do DNA molecules compare to the cells theyre in?

Answer 3

DNA molecules are much larger than the cellular packages that contain them

Question 4

give some characteristics of viruses

Answer 4

o Single or double stranded DNA or RNA organisms
o These strands are small, RNA genomes are 9000 bases and DNA varies between 5000-500,000 base pairs

Question 5

what is the genetic makeup of bacteria

Answer 5

Double stranded DNA based organisms with genetic info contained in circular chromosomes usually just one

Question 6

describe bacterial chromosomes

Answer 6

Bacterial chromosomes have a high density of genes the majority of which encodes for proteins for the purpose of reproduction

Question 7

describe the genetic layout of the chromosomes

Answer 7

The Genes are uninterrupted in sequences unlike eukaryotic codons leading to simpler transcriptions

Have operons which are sequences of several genes co-transcribed with related functions

Question 8

what are plasmids?

Answer 8

These are self replicating and autonomous genetic info carried in addition to an organisms DNA

Question 9

explain why plasmids can be useful

Answer 9

 Confer no guaranteed advantage and can be non-essential genes that may help in hosts depending on environments
 This makes them important molecular bio tools
 They encode for many antibiotic resistance or toxin genes making them important to us too

Question 10

how large are plasmids

Answer 10

typically 2000-10000 base pairs

Question 11

where are plasmids found?

Answer 11

Yeast, fungi, bacteria

Question 12

describe the genetic layout of Eukaryotes

Answer 12

o Genetic material in multiple linear chromosomes contained in cells
o These chromosomes differ greatly in length
o Diploid setup as they contain two sets of chromosomes one from each parent
o Genes on each chromosome can differ to greater or lesser extents if at all

Question 13

what make eukaryotic genetic makeup more complicated than other groups

Answer 13

 Contain exons (coding sequences) and introns (non-coding sequences which are spliced out)
 Splicing patterns of introns between exons leads to many products being made from one gene

Question 14

Why is DNA packaging necessary?

Answer 14

a whole DNA strand is far far longer unwrapped than the cell it is contained in and without proper packaging wouldnt fit

Question 15

describe the way DNA is packaged in human cells

Answer 15

DNA supercoils from a long double helix strand into a more compact form

Question 16

what are the two different ways of supercoiling?

Answer 16

• Plectonemic- basic twists
• Solenoidal- telephone wire ‘loop-twists’ that are more space effective

Question 17

why is supercoiling a problem and how is it fixed?

Answer 17

 Replication and transcription are affected and affect DNA supercoiling due to gene access in coils being difficult
 Topoisomerases catalyse changes in DNA supercoiling by ‘cutting’ supercoiled DNA

Question 18

describe what makes up chromatins

Answer 18

 Made of DNA and Proteins
 Histones at the core of nucleosomes
 Nucleosomes are the fundamental organisational units of chromatin

Question 19

how do chromatin contents make up a chromosome?

Answer 19

 histones with DNA are packed into successively higher order structures DNAsupercoilshistoneshistone coils (30nm fibers) …
 This eventually builds into a compact two-chromatid chromosome

Question 20

how does packaging in bacteria compare to eukaryotes?

Answer 20

Bacterial DNA is also highly compacted but less organized