DNA,genes And Chromosomes

Question 1

Chromosomes in Prokaryotes

Answer 1

They lack a nucleus or membrane bound organelles

Question 2

Chromosomes in Eukaryotes

Answer 2

It has a membrane bound nucleause with linear chromosomes

Question 3

Locus

Answer 3

Fixed position of a gene on a DNA molecule

Question 4

What holds tightly coiled DNA in place?

Answer 4

Histones

Question 5

What do Histones and DNA form?

Answer 5

The proteins help to support DNA and fix it in position
Forms a DNA-Histone complex which then coils more

Question 6

What do chromosomes consist of?

Answer 6

2 chromatids and one centromere

Question 7

Describe DNA molecules in mitochondria in chloroplasts

Answer 7

Shorter than in nucleus
Circular not linear
Not associated with Histones proteins
Similar to prokaryotic DNA

Question 8

Describe DNA in prokaryotes

Answer 8

Circular not linear
Can be called a bacterial chromosome
Shorter
Not associated with Histones
It fits into the cell by coiling tightly-supercooling

Question 9

What is a gene

Answer 9

A base sequence of DNA that codes for amino acid sequence of a polypeptide or a functional RNA

Question 10

What is a functional RNA?

Answer 10

Descríbeles RNA molecules (other than mRNA) which perform specific functions during protein synthesis
E.g. tRNA and rRNA-forms part of chromosome

Question 11

Alleles

Answer 11

More than one form of a gene
The order of bases is slightly different in each so they code for different versions of the same polypeptide

Question 12

Homologous chromosomes

Answer 12

One of each pair of chromosomes is provided by the mother, and the other the father

Question 13

diploid number of chromosomes in humans

Answer 13

46

Question 14

Number of chromosomes in sperm and egg cells

Answer 14

Haploid-23

Question 15

What is the triplet code?

Answer 15

3 DNA bases code for one amino acid

Question 16

Why is the genetic code known as degenerate?

Answer 16

Because most amino acids have more than one triple code
Most have between 2 and 6

Question 17

what directions are the triplet codes read in?

Answer 17

Always read in one direction along the DNA strand

Question 18

Stop codes

Answer 18

Three triplet codes that dont code for any amino acid
They mark the end of the polypeptide chain

Question 19

Give 2 other features of the genetic code other than it is degenerate

Answer 19

Non-overlapping- each base in the sequence is only read once
Universal- the same in all organisms

Question 20

What is a codon?

Answer 20

The 3 complementary bases (to the triplet code on DNA) on mRNA

Question 21

Some genes dont code for polypeptides. What do they code for?

Answer 21

Functional RNA e.g. rRNA tRNA

Question 22

Introns

Answer 22

Sections of genes that dont code for amino acids
They are removed in protein synthesis so they dont affect the amino acid sequence
Prokaryotic DNA doesnt have them

Question 23

Exons

Answer 23

The parts of the gene that do code for amino acids

Question 24

Genetic code

Answer 24

Is carried on dna

Question 25

How will the protein structure be affected if there is changes to the base sequence on the DNA molecule?

Answer 25

The triplet code on the DNA changes
Leads to a change in the sequence of amino acids/primary structure of protein
Bonds form in different places, primary structure folds differently
Changes the tertiary structure of a protein/shape of the active site of enzyme