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Biology Alevels > Genetics Topic 4 > Flashcards

Genetics Topic 4 Flashcards

1
Q

What are the 3 features of genetic code

A
  1. Degenerate
  2. Universal
  3. Non over lapping
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2
Q

What does degenerate mean

A

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

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3
Q

What are exons and introns

A

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

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4
Q

What is a codon

A

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

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5
Q

What is a genome

A

An organisms complete set of genes in a cell

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6
Q

What is transcription

A

Is the production of mRNA from DNA

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7
Q

What is translation

A

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

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8
Q

Describe-what happens before transcription

A

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

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9
Q

Describe transcription

A

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

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10
Q

what is non disjunction

A

when chromatids or chromosomes do not split equally during anaphase

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11
Q

what is polyploidy

A

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

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12
Q

what is aneuploidy

A

changes in the number of individual chromosomes

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13
Q

define meiosis

A

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

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14
Q

what is courtship behaivour

A

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

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15
Q

What happens during meiosis one

A

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

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16
Q

What happens during meiosis 11

A

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

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17
Q

Give two ways meiosis produces genetic variation

A

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

Results in New combinations of alleles

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18
Q

What is genetic diversity

A

The total number of different alleles in a population

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19
Q

What is directional selection

A

-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

20
Q

How does antibiotic resistance in crease directional selection

A

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

21
Q

What is stabilising selection

A

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

22
Q

Define species

A

A group of organisms which can breed to make fertile offspring

23
Q

Define classification

A

The process of arranging organisms into groups

24
Q

Define biodiversity

A

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

25
Q

Community

A

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

26
Q

What is the difference in DNA between eukaryotes and prokaryotes

A

Eukaryotes
Linear DNA
Associated with protein
Contained in nuclear membrane

Prokaryotes
Circular DNA
Not associated with proteins
Not contained in a membrane

27
Q

Describe the DNA in mitochondria and chloroplast

A

Have circular DNA

28
Q

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

A

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

29
Q

What does universal mean

A

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

30
Q

What does non-overlapping mean

A

Base triplets don’t overlap or share their bases

31
Q

What is the proteome

A

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

32
Q

What is translation

A

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

33
Q

Describe the process of translation

A
  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
  2. The amino acids they carry are joined by the ribosome
  3. This continues until the ribosome meets a codon called a “stop” codon and the signals for translation to stop and the polypeptide to detach
34
Q

What is genetic diversity

A

The number of different alleles in a population

35
Q

How can you improve genetic diversity

A

New mutations
Through migration of a new population

36
Q

What are the steps of natural selection

A
  1. Random mutations result in new alleles
    2.individuals may have an allele that gives them a reproductive advantage
  2. 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
  3. Overtime allele frequency in population increases
37
Q

What is biodiversity

A

Refers to the variety of different organisms

38
Q

What is species richness

A

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

39
Q

What is the index diversity

A

DI=N(n-1)/(n-1)

N=the total number of organisms
n=the total number of organisms of each species

40
Q

How can biodiversity be reduced

A

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

41
Q

How can we improve agriculture whilst conserving biodiversity

A

Protect endangered species

Provide subsidies

Restrict development of areas

42
Q

How are organisms classified according

A

Phylogenic classification system

43
Q

What is hierarchies for phylogenic system

A

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

44
Q

What are the humans genus and species

A

Genus :Homo
Species:Sapiens

45
Q

What is courtship behaviour

A

Courtship behaviours are used to help classify species

Organisms use courtship behaviour to attract a mate from the right species

46
Q

What does courtship behaviour tell you about a species

A

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

Biology Alevels (13 decks)

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