Genetics Topic 4

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

Is the production of mRNA from DNA

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 ,pre-mRNA introns are spliced out , then the mRNA moves out of the pore and 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

Define biodiversity

Answer 24

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

Question 25

Community

Answer 25

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

Question 26

What is the difference in DNA between eukaryotes and prokaryotes

Answer 26

Eukaryotes Linear DNA Associated with protein Contained in nuclear membrane Prokaryotes Circular DNA Not associated with proteins Not contained in a membrane

Question 27

Describe the DNA in mitochondria and chloroplast

Answer 27

Have circular DNA

Question 28

Describe the link between DNA and genes and bases with amino acids

Answer 28

DNA contains genes Genes are sequences of DNA that code for an amino acid Every three bases in the DNA code for a different amino acid

Question 29

What does universal mean

Answer 29

The same base sequence codes for the same amino acid in different organism

Question 30

What does non-overlapping mean

Answer 30

Base triplets don’t overlap or share their bases

Question 31

What is the proteome

Answer 31

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

Question 32

What is translation

Answer 32

The production of polypeptides from the sequence of codons carried by mRNA

Question 33

Describe the process of translation

Answer 33

1. the mRNA attaches itself to a ribosome and the tRNA brings the amino acid 2.A tRNA molecule that has a complementary anticodon for the first codon on the amino acid binds to it 3.Another tRNA that is complementary for the second codon binds 4. The amino acids they carry are joined by the ribosome 5. This continues until the ribosome meets a codon called a “stop” codon and the signals for translation to stop and the polypeptide to detach

Question 34

What is genetic diversity

Answer 34

The number of different alleles in a population

Question 35

How can you improve genetic diversity

Answer 35

New mutations Through migration of a new population

Question 36

What are the steps of natural selection

Answer 36

1. Random mutations result in new alleles 2.individuals may have an allele that gives them a reproductive advantage 3. These individuals are more likely to survive and pass on their gene whereas individuals with a different allele is less advantageous will be less likely to survive 4. Overtime allele frequency in population increases

Question 37

What is biodiversity

Answer 37

Refers to the variety of different organisms

Question 38

What is species richness

Answer 38

Is a measure of the number of different species in a community

Question 39

What is the index diversity

Answer 39

DI=N(n-1)/(n-1) N=the total number of organisms n=the total number of organisms of each species

Question 40

How can biodiversity be reduced

Answer 40

Monocultures -only a small number of organisms can be supported Using pesticides -to kill insects reduces number of insects and animals which feed on the insects could die Using herbicides -reduces the number of weeds ,organisms which feed on weeds could die Removing hedgerows - destroys habitat for organisms that live there

Question 41

How can we improve agriculture whilst conserving biodiversity

Answer 41

Protect endangered species Provide subsidies Restrict development of areas

Question 42

How are organisms classified according

Answer 42

Phylogenic classification system

Question 43

What is hierarchies for phylogenic system

Answer 43

domain, kingdom, phylum, class, order, family, genus, and species

Question 44

What are the humans genus and species

Answer 44

Genus :Homo Species:Sapiens

Question 45

What is courtship behaviour

Answer 45

Courtship behaviours are used to help classify species Organisms use courtship behaviour to attract a mate from the right species

Question 46

What does courtship behaviour tell you about a species

Answer 46

The more closely related species are, the more similar their courtship behaviour