3.4.1 & 3.4.2 DNA, Genes Ans Chromosomes And Protein Snythesis

Question 1

What is the Endosymbiotic theory?

Answer 1

Bacteria(prokaryotic cell) fused with host cell and became encased in a vesicle- this bacteria became a mitochondrial

Question 2

What is a gene?

Answer 2

Section of DNA on a chromosome coding for one or more polypeptide

Question 3

What is an allele?

Answer 3

One of a number of alternative forms of a gene

Question 4

What is a locus?

Answer 4

The position of a gene on a chromosome/DNA molecule

Question 5

What is a homologous chromosome?

Answer 5

A pair of chromosomes, one material and one paternal, they have the same gene and loci so they have the same features

Question 6

What do genres code for?

Answer 6

One or more protein(polypeptide)

Question 7

What is a codon?

Answer 7

3 DNA base letters making a triplet

Question 8

What does each codon code for?

Answer 8

One specific amino acid

Question 9

Why wouldn’t a doublet code work?

Answer 9

Not enough combinations (16 not 64)

Question 10

What is a non-coding and coding gene called?

Answer 10

Non-coding: Introns- they interrupt the sequence

Coding- Exons- expressed sequence

Question 11

Why is the genetic code describe as degenerate, universal and non overlapping

Answer 11

Degenerate:
Most amino acids are coded for by more than one triplet
First 2 bases are more important than the 3rd in specifying the amino acid
There are start and stop codons

Universal:
Each triplet codes for the same amino acid in all organisms(few exceptions)
Indirect evidence for evolution
Allows genetic engineering

Non overlapping:
It’s not overlapping….

Question 12

How does transcription work ?

Answer 12

Enzyme DNA helices acts on a specific region of DNA breaking the H bonds exposing the bases

RNA polymerase binds to the DNA and as it moves along the strand it picks up free nucleotides in the nucleoplasm

The nucleotide bases on the template strand pair with the complementary nucleotide bases(only 12 at a time)

RNA polymerase reaches stop codon then it detaches and pre mRNA is complete

Question 13

What happens to pre mRNA in the nucleus?

Answer 13

It’s spliced to remove introns that don’t code for amino acids
This doesn’t happen in prokaryotic cells

Question 14

What then happens to the mRNA?

Answer 14

Leave through nuclear pore and attaches itself to a ribosome consisting of ribosomal RNA and protein

Question 15

What is translation?

Answer 15

Process where condoms on mRNA are translated into a polypeptide

Question 16

How does translation work?

Answer 16

Ribosome becomes attached to to starting codon

tRNA with complimentary anti codon sequence moves to ribosome and pairs up with mRNA codon

Another tRNA molecule pairs with next codon(codes for different amino acid)

Ribosome moves along mRNA brining together 2 tRNA molecules at a time, each pairing with mRNA codon

2 amino acids on tRNA and joined by peptide bonds(using ATP and a ribosomal enzyme)

Ribosome moves to 3rd codon on mRNA linking amino acids on the 2nd and 3rd tRNA molecules

1st tRNA released and collects other amino acids

Process continues until reached at stop codon

Question 17

What is a genome and what is a proteome?

Answer 17

Genome:
Group of genes that show a trait

Proteome:
Trait that is expressed by a genome