Gene Expression

Question 1

What is a genome

Answer 1

The complete set of genetic material within the chromosomes of an organisms. Every somatic cell (other than the blood cell) has a complete genome

Question 2

Gene / Structural gene

Answer 2

A segment of DNA that carrys the instruction / code for the production of a protein that will eventually produce a phenotype

Question 3

allele

Answer 3

a form of a gene that is located in the same position on a homologous chromosome that code for the same protein e.g. allele for eye
a single individual can carry a maximium of two different alleles for the same protein

Question 4

gene expression

Answer 4

the transfer of the genetic code from DNA to be translated into a protein - genotype giving rise to a phenotype

Question 5

Types of Non-Coding DNA

Answer 5

• Regulatory genes - that produce transcription factors
• telomeres that cap the ends of chromosomes
• centromeres where chromatids are attached
• RNA coding regions which create mRNA,tRNA, rRNA
• introns which are copied by RNA but later spliced

Question 6

Process of translation

Answer 6

1. RNA polymerase binds to DNA just before the start of the gene at the promoter region and unzips it.
2. It begins adding complementary RNA nucleotides (Uracil instead of thymine) at the start codon in the same direction as DNA Polymerase (5’ to 3’), rezipping behind it and unzipping ahead as it moves up the strand.
3. Once it reaches the end of the gene and a stop codon is added, RNA polymerase and the newly formed mRNA detach and the DNA strand rezips

Question 7

Codons

Answer 7

Triplets of nucleotides on mRNA coding for an amino acid

Question 8

Post-transcriptional modification process in eukaryotes

Answer 8

1. non - coding introns are removed
2. coding exons are re-joined to form mature mRNA
3. excess nucleotides are trimmed and a methyl-guanine cap and long adenine tail is added for stability when mRNA binds with the ribosome

Question 9

Translation Process

Answer 9

1. mRNA moved out of the nuclues and binds with a ribosome in the cytoplasm
2. tRNA with an anticodon on one end an amino acid on the other moves to the ribosome and binds to the first codon on the mRNA strand
3. This step is repeated and amino acids form peptide bonds to come together and eventually form polypetide chains of proteins.

Question 10

How is gene expression regulated so that every cell in the body doesn’t produce every protein

Answer 10

The genes relevant to that cell are switched on (meaning the DNA is loosened from the histones and the genetic code is exposed) whereas the the irrelevant genes are tightly bound around histones and RNA polymerase is unable to initiate transcription

Question 11

Transcription factors

Answer 11

Protein produced by regulatory genes that control gene expression

Question 12

Transcription Factor Action

Answer 12

They attach to the start of a structural gene either blocking the attachment of RNA polymerase or altering the rate at which mRNA is produced

Question 13

Epigenitic Control of Gene expression

Answer 13

Factors outside of the gene that affect gene expression

Question 14

Example of a pyschological epigenetic factor that affects gene expression

Answer 14

Parental care:
more parental care could lead to more expression of the stress tolerance gene leading to lower stress levels and vice versa

Question 15

what are Hox transcription factors

Answer 15

Hox protein produced by Hox genes that regulate the type of appendages that will form on a segment - they regulate the morphology of plants and animals

Question 16

SRY (sex-determining region Y) Gene action

Answer 16

produces a transcription factor that binds to other genes and promotes the production of the SRY protein which start the process to develop testes in foetus