DNA

Question 1

What are DNA molecules?

Answer 1

Large and complex molecules which carry the genetic code that determine the characteristics of a living organism

Question 2

What are genes

Answer 2

A gene is a section of DNA that codes for a specific protein
Unit of heredity

Question 3

What is a chromosome

Answer 3

A thread-like, gene carrying structure made of protein and DNA by which hereditary information is physically passed from one generation to the next

Question 4

How many chromosomes do we have?

Answer 4

23 pairs

Question 5

What is a genome

Answer 5

Entire DNA of an organism

Question 6

What is a homologous pair

Answer 6

A pair of chromosomes, one from each parent, containing similar values

Question 7

What are alleles

Answer 7

Different versions of the same gene

Only one allele is expressed

Question 8

What is a genotype

Answer 8

The collection of alleles that determine the characteristics and can be expressed as a phenotype

Question 9

Name the nucleotides

Answer 9

Adenine, guanine, thymine, cytosine

Question 10

What is a nucleotide

Answer 10

A building block of DNA consisting of 5 covalently bonded sugars to an organic gas and phosphate group

Question 11

Complementary base pairing

Answer 11

Adenine and thymine - 2 hydrogen bonds

Cytosine and guanine - 3 hydrogen bonds

Question 12

Differences between RNA and DNA

Answer 12

RNA = single stranded
Contains uracil instead of thymine
RNA contains ribose, DNA contains deoxyribose

Question 13

Name the 2 types of RNA

Answer 13

mRNA - messenger RNA

tRNA - transfer RNA

Question 14

What does mRNA do

Answer 14

Forms a copy of the DNA code

Question 15

What does tRNA do

Answer 15

Carries amino acids to ribosomes

Question 16

Describe transcription

Answer 16

DNA double helix unwinds
Free RNA nucleotides complimentary base pair with the template strand
Polymerised (by RNA polymerase) to form mRNA
Double helix will rewind
mRNA moves to next step

Question 17

Describe translation

Answer 17

• mRNA strand travels through cytoplasm and attaches to ribosome
• Codon of mRNA complimentary base pairs with anticodon of tRNA
• tRNA molecules transport specific amino acids to the ribosome which they leave behin shortly after lining up opposite DNA
• Used tRNA molecules exit ribosome and collect another specific amino acid
• A chain of several hundred amino acids in correct order according to the original DNA is then made - called polypeptide

Question 18

What is a mutation

Answer 18

An alteration in the nucleotide sequence of the genome of an organism

Question 19

What is duplication

Answer 19

Nucleotide is underrated twice instead of once

Entire base sequence is altered

Question 20

What is deletion

Answer 20

Nucleotide is missed out
Entire base sequence is altered
Whole gene is different

Question 21

What is substitution

Answer 21

Different nucleotide is used
Codes for different amino acid
Significant alteration in the functionality of a protein or total lack of function may occur

Question 22

What is an inversion

Answer 22

Sequence of the bases in a triplet is reversed
Effects similar to substitution
Only one triplet is affected

Question 23

Factors that increase the likelihood of mutations:

Answer 23

1) sunlight and skin damage (UV radiation)
2) smoking (distorts shape of DNA molecule)
3) ionising radiation (gamma rays and X-rays)

Question 24

Homozygous

Answer 24

Both alleles present are the same

Question 25

Heterozygous

Answer 25

Both alleles present are different

Question 26

Genotype

Answer 26

What alleles are present in an organism

Question 27

Phenotype

Answer 27

‘Outward’ expression of the genotype

Question 28

What is codominance

Answer 28

Both alleles contribute to the phenotype

Question 29

What can a change in DNA do

Answer 29

Affect the phenotype by altering the sequence of amino acids in a protein

Question 30

What are monohybrid crosses

Answer 30

Genetic crosses of single gene combinations