Genetics

Question 1

What are the 3 features of genetic code

Answer 1

1. Degenerate
2. Universal
3. Non over lapping

Question 2

What does degenerate mean

Answer 2

There are more than one triplet bases which code for each amino acid

Question 3

What are exons and introns

Answer 3

Exons : sequences of DNA that do code for amino acid
Introns : section which does not code for amino acid

Question 4

What is a codon

Answer 4

Three bases on MRNA which code for a specific amino acid

Start codon -the three bases at the start of every gene which intimates translation

Stop codon - three bases at the end of every gene where ribosomes detach at end of translation

Question 5

What is a genome

Answer 5

An organisms complete set of genes in a cell

Question 6

What is transcription

Answer 6

Where one gene on DNA is copied onto mRNA.

Question 7

What is translation

Answer 7

Where the mRNA joins with a ribosome, and corresponding tRNA molecules bring the amino acids the codons code for

Question 8

Describe-what happens before transcription

Answer 8

A complementary mRNA copy of a gene is created in nucleus
mRNA is shorter than DNA so is able to carry the genetic code to the ribosome

Question 9

Describe transcription

Answer 9

1.DNA helix unwinds exposing DNA bases
2.) unwinding is catalysed by DNA helicase are which breaks hydrogen bonds between bases
3.) free mRNA nucleotides in nucleus align opposite exposed complementary DNA bases
4.)RNA polymerase joins together RNA nucleotides to create RNA polymer chain.
5.in eukaryotic cells ,introns are spliced out , then the mRNA moves out of the poreand attaches to a ribosome in the cytoplasm

Question 10

what is non disjunction

Answer 10

when chromatids or chromosomes do not split equally during anaphase

Question 11

what is polyploidy

Answer 11

changes in the whole set of chromosomes occur when organisms have two or three more chromosomes rather than usual two

Question 12

what is aneuploidy

Answer 12

changes in the number of individual chromosomes

Question 13

define meiosis

Answer 13

is a form of cell division which gives rise to four genetically different daughter cells. produces haploid cells

Question 14

what is courtship behaivour

Answer 14

Members of the same species share similar physical and
behavioural characteristics. Courtship behaviour takes place before mating.

Question 15

What happens during meiosis one

Answer 15

1.) the homologous pairs for bivalvents
2.crossing over of chromosomes (exchange of genetic material)happens during chiasma
3.) cell divides into two ,homologous chromosomes separate randomly

Question 16

What happens during meiosis 11

Answer 16

1.)Independent segregation of sister chromatids
2.)each cell divides again ,producing haploids

Question 17

Give two ways meiosis produces genetic variation

Answer 17

1.) crossing over during meiosis one
2. Independent segregation

Results in New combinations of alleles

Question 18

What is genetic diversity

Answer 18

The total number of different alleles in a population

Question 19

What is directional selection

Answer 19

-occurs when environmental conditions change
-individuals with phenotypes suited to the new conditions will survive and pass on genes
-overtime the mean will move towards the characteristic

Question 20

How does antibiotic resistance in crease directional selection

Answer 20

Bacteria with the mutation is able to survive and reproduce.
This increases the allele frequency and the population will shift to have greater anti biotic resistance

Question 21

What is stabilising selection

Answer 21

When environmental conditions stay the same
Individuals closest to the mean are favoured
And any new selection is selected against

Question 22

Define species

Answer 22

A group of organisms which can breed to make fertile offspring

Question 23

Define classification

Answer 23

The process of arranging organisms into groups

Question 24

Two components of binomial system

Answer 24

Generic name - the genus the organisms belong to . Closely related species share same genus
Specific name -the species organisms belong to

Question 25

Define biodiversity

Answer 25

The variety of living organisms
Measured in species diversity
Genetic diversity
Ecosystem diversity

Question 26

Community

Answer 26

All the different species live in the same area and interact with one another