Genetics

Question 1

Explain the structure of DNA

Answer 1

-Pentose sugar
-Nitrogenous base
-Phosphate group

Question 2

Explain what Cytosine and thymine are

Answer 2

• Are single carbon nitrogen rings called pyrimidines

Question 3

Explain what adenine and guanine are

Answer 3

Double carbon rings called purines

Question 4

Explain the watson and crick theory

Answer 4

• They proped the Double helix model
  -DNA is in a twised ladder with chemical bonds
  -The side of the ladder is composed of a sugar and phosphate group, held togeehr by strong phosphodiester bonds

Question 5

Explain the process of DNA coiling

Answer 5

• DNA is wrapped aroud histones to form nucleosomes
  -Nuclesomes form helical solenoids
  -Solenoids are organised into chromatin loops , each with 100,000 base pairs

Question 6

Explain the process of DNA replication

Answer 6

• The weak hydrogens break,produicng 2 single strands with their unpaired bases
• Each single strand acts as a template for making a complementary strand
  -DNA polymerase adds free nucleotides to the 3 end of the strand
• DNA polymerase performs part of a proofreading procedure, checking if the newly added nucloetides are complementary to the templte base

Question 7

What is the function of replication bubbles

Answer 7

Allow DNA replication to take place at multiple locations on the chromosme, speeding up the replication process

Question 8

Where does DNA formation and replicaiton occur

Answer 8

Cell nucles

Question 9

Where does protein synthesis occur

Answer 9

cytoplasm

Question 10

Explain the structure of RNA

Answer 10

• ribose sugar
• uracil instead of thymine
  -single stranded

Question 11

What is transcription , breif statment

Answer 11

The process where a messenger RNA(mRNA) is synthesized from a DNA template

Question 12

Explain the process of RNA + modified cap

Answer 12

-RNA polymerase II binds to the promotor site on the DNA, initiating contraction
-DNA polymerase seperatez the DNA strand leaving the bases exposed
-One strand acts as a template
-RNA Polymerases moves along the template in a 3 - 5 direction, creating a complementary strands in the 5- 3 direction

• As transcription progresses, the 5 end of the RNA gets as modified cap , to prevent degredation of the RNA molecule

Question 13

When does transcriptione end

Answer 13

When the polymerase reaches the termination sequence

Question 14

What are general transcription factors

Answer 14

Proteins that are required for the transcription of all genes

Question 15

What are specific transcription factors

Answer 15

Proteins that activate certain genes

Question 16

What is the function of RNA polymerase

Answer 16

It is a key enzyme in trancription, binding to the promtor region to initiate transcrition, but it cannot
- Locator the promotor region on its ownr
-produces significant amounts of RNA without assistance

Question 17

What does effectove transcripiton require

Answer 17

It requires the interaction of around 50 proteins including
-Genral transcription factors, which bind to RNA polymerase and specific DNA sequences in the promotor region

Question 18

Explain enhancers

Answer 18

• Loacted far from the gene, they increase transcriptional activity of a specific gene
  -They do not directly interact with genes, but are bound by activators

Question 19

What do activators bind to

Answer 19

Bind to coactivators, which then bind to general transcription factor compleses

Question 20

What are silencers

Answer 20

• oppsoite effect to enhancers
• They repress the gene transcription through similar interactoms

Question 21

What can mutations in enhancers, silencers,promotors or transcriptonal factors lead to

Answer 21

• Genetic diseass

Question 22

How do transcription factors loacte the specific DNA sequencse

Answer 22

• DNA binding motifs

Question 23

What is gene expression influenced by

Answer 23

• Several epigenetic modifications including:
• Chromatin structure
  -Histone acetylation
  -DNA methylation and micor NAs

Question 24

Where does spliving occur and describe the process

Answer 24

• In eukaryotes-nucleus
• The introns are removed from the primary RNA and then the exons are joined togther to create function mRNA
• The mRNA transcript then leaves the nucleus and moves to the cytoplasm for protein synthesis

Question 25

What can errors in gene splicing lead to

Answer 25

- Genetic mutations , which may result in diseases

Question 26

What does alternate splicing allow

Answer 26

It allows a single gene to produce multiple protein products by splicing the primary transcipt in various wyas `

Question 27

Explain why the gentic code can be seen as degenerate

Answer 27

- As the genetic code consits of 64 possible codons with 3 being stop codons and 61 codons remaining to specifcy 20 amino acids, making the code degenerate as most amino acids are coded by multiple codons

Question 28

Why is the genetic code NEARLY universal

Answer 28

As the mitochondiral DNA has some codons differing from the nuclear DNA

Question 29

What happens in translation( brief statment)

Answer 29

- It uses mRNA as a template to synthesis a polypeptide

Question 30

What is the role of tRNA in translation

Answer 30

Each tRNA binds to a spcecific amino acid and has an anticodon sequcne that is complementary with the mRNA cododn

Question 31

What is the role of ribosomes in translation

Answer 31

- It binds to mRNA and tRNA faciliating codon by codon reading and peptide bond formation between the amino acids

Question 32

When does translation end

Answer 32

It ends when the ribosomes encounters a stop codon on the mRNA releasing the completed polypeptide

Question 33

Name the different types of RNA

Answer 33

-MicroRNAS( miRNA) -Small interfering rNA( siRNA) -Long Noncoding RNA

Question 34

What is noncoding DNA

Answer 34

RNAs that do not translate into proteins

Question 35

What is the function of microRNAs(miRNA)

Answer 35

They down regulate mRNA expression by binding to specific mRNA targets

Question 36

What is the function of small interfering RNA (siRNA)

Answer 36

They target single specifc mRNA used in cancer genes

Question 36

What is the function of Long Noncoding RNA

Answer 36

- They are involved in gene regulation such as X chromosome inactivation in females