Unit 4 - DNA genes and chromosomes, DNA and protein synthesis, Genetic diversity and meiosis

Question 1

DNA Points Eukaryotes

Answer 1

Linear DNA 
Long
Exist as chromosomes
Located in the nucleus 
Wound around histone proteins

Question 2

Which organelles in eukaryotic cells have their own DNA?

Answer 2

Mitochondria

Chloroplasts

Question 3

Prokaryote DNA points

Answer 3

Circular DNA
No histones
Short
No introns

Question 4

Gene definition

Answer 4

A sequences of DNA bases that codes for:
A poly peptide
Or a functional RNA molecule

Question 5

Why do some genes not code for polypeptides?

Answer 5

They are introns

Question 6

Transcription

Answer 6

DNA helicase activity (of RNA polymerase) breaks H bonds separating strands
RNA polymerase joins complementary RNA nucleotides to make a complementary copy of the template streand
Once a stop signal is reache, the pre mRNA detaches from the DNA
Removes introns from pre mRNA and joins exons to make mature RNA
Leaves via nuclear pore

Question 7

Translation

Answer 7

A ribosome attaches to start codon
A complementary tRNA molecule moves and pairs up with sequence on mRNA
A complementary tRNA binds with the next codon
By means of an enzyme and ATP a peptide bond is formed between the 2 amino acids
Ribosome moves onto third codon + same process occurs
As this happens the first tRNA molecule is released from its amino acid and is free to picl up another one
Process continues this way
Until stop codon is reached- ribosome, mRNA and last tRNA molecule all separate- polypeptide chain is complete

Question 8

3 characteristics of DNA

Answer 8

Universal
Non overlapping
Degenerate

Question 9

Genome

Answer 9

Complete set of genes present in the cell

Question 10

Proteome

Answer 10

The full range of proteins that a cell is able to produce

Question 11

meiosis

Answer 11

Before meiosis DNA unravels and replicates so their are two copies of each chromosome
The DNA condenses to form double-armed chromosomes each made from 2 sister chromatids
Meiosis 1- Chromosomes arrange themselves into homologous pairs (Bivalent) They are then separated (Same as mitosis except homologous pairs are separated instead of sister chromatids)
Meiosis 2- The pairs of sister chromatids that make up each chromosome are separated by centromere (Same as mitosis)
Four haplod cells, genetically different are produced

Question 12

2 reasons why meiosis produces cells that are genetically different

Answer 12

1- Crossign over in meiosis 1 in bivalent

2- Independent segregation in meiosis 1

Question 13

Non disjunction meaning

Answer 13

Chromosome 21 fails to separate propperly during meiosis

Question 14

What is down syndrome caused by

Answer 14

Extra 21 chromosome

Question 15

Types of mutation errors

Answer 15

Substitution

Deletion

Question 16

Why do not all mutations cause changes in amino acid sequence

Answer 16

DNA is degenerate

Question 17

Examples of mutagenic agents

Answer 17

UV radiation
Ionising radiation
Chemicals
Viruses

Question 18

Meiosis vs mitosis

Answer 18

4 daughter cells vs 2 daugter cells 
Haploid cells vs diplod cells
2 Divisions vs 1 division 
Forms bivalent vs no bivalent 
Diffferent vs identical
Independant segregation vs no independant segregation
Crossing over vs no crossing over

Question 19

Transcription

Answer 19

Question 20

Translation

Answer 20