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Biology > Genetic Information, variation and relationships between organisms > Flashcards

Genetic Information, variation and relationships between organisms Flashcards

1
Q

What are eukaryotic cells structure in nucleus

A

DNA molecules very long
Associated with proteins - histones
DNA molecule associated proteins form chromosome

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2
Q

What are prokaryotic cells structure

A

DNA molecules short, circular

Not associated with proteins

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3
Q

What else within eukaryotic cells contain DNA and what is it like

A

Mitochondria and chloroplasts

Like DNA of prokaryotes- short, circular, not associated with proteins

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4
Q

What do DNA base sequences code for

A 
Amino acid sequence of polypeptide 
Functional RNA (including RNA, tRNAs)
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5
Q

What shape is tRNA

A

Clover leaf shape
Single stranded
Shortest strand

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6
Q

What does the anticodon determine of the tRNA molecule

A

Which amino acid carried

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7
Q

How do tRNA molecule ps have paired bases

A

Due to folding

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8
Q

Which strand is most stable mRNA or tRNA

A

tRNA

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9
Q

What does mRNA do

A

Changes DNA to RNA

Moved out of nucleus to ribosome

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10
Q

What is the mRNA strand like

A

Single long strand

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11
Q

What do the codons on mRNA do

A

Code for amino acids to make proteins

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12
Q

What are the similarities of DNA and mRNA

A

Triplet codons
Sugar phosphate backbone
Made of single nucleotide

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13
Q

What is the difference in bases between DNA and RNA

A

DNA - A,T,C,G

RNA - A,U,C,G

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14
Q

When are chromosomes visible

A

As distinct structures when cell dividing

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15
Q

What are chromosomes made of - two threads

A

Chromatid joined at centromere

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16
Q

What is a gene

A

Section of DNA

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17
Q

What is a locus

A

Fixed position on gene on chromosomes

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18
Q

What is the degenerate code

A

Most amino acids coded for by more than one triplet

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19
Q

What does non overlapping mean

A

Counts DNA in triplet codons

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20
Q

What is good about the genetic code

A

Universal

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21
Q

What are non coding parts of DNA called

22
Q

What is transcription, what happens a particular type of cell

A

Formation of mRNA from DNA

In eukaryotic cells causes formation of pre-mRNA

23
Q

What does the enzyme DNA helicase do

A

Acts on specific DNA region, two strands separate by breaking hydrogen bonds, expose nucleotide bases in region

24
Q

Where do the free mRNA nucleotide bases attach to

A

Template strand by complementary base pairing

25
What does RNA polymerase do
Move along mRNA strand forming sugar phosphate backbone
26
What happens when a stop code is reached
Transcription stops, strand pre-mRNA made
27
What happens in splicing
DNA of eukaryotic cell gene made of exons and introns Introns prevent polypeptide synthesis as don't code for proteins Base sequence corresponding to introns removed Functional exons joined
28
Why doesn't splicing occur in prokaryotes
DNA gene sequence doesn't contain introns
29
What happens to the mRNA after being spliced
Leaves nucleus out nuclear lire | Translation - mRNA attaches to ribosome in cytoplasm, becomes attached to starting codon
30
What is a tRNA molecule made of
Specific amino acid at top, anticodon (triplet codon) at bottom
31
How does the tRNA molecule bind the the mRNA strand and where
Complementary base pairing of codons Dorothy anticodon-codon complex at ribosome
32
Why is ATP used in translation
To form peptide bond between amino acids uses ATP which is hydrolysed to provide energy
33
What happens to the tRNA when it is released from its specific amino acid at ribosome
Free to collect another amino acid at its amino acid binding site
34
What happens when stop code reached
Polypeptide synthesis stops and last tRNA separates | Form tertiary structure - disulphide bonds, hydrogen bonds, ionic bonds
35
What can cause gene mutations
Base deletion and base substitution
36
Why does base substitution not always cause mutations
Degenerate code
37
What is a mutagenic agent
Can increase rate of gene mutation
38
What is meiosis
Cells division that makes four genetically different games
39
What happens during meiosis
1. DNA replicated 2. Independent segregation 3. Crossing over 4. Homologous pairs separate to opposite poles of cell 5. Form four genetically different haploid cells
40
Why are sex cells haploid
So diploid number restored at fertilisation
41
How does meiosis cause genetic variation
Crossing over and independent segregation
42
What is crossing over
New combinations of maternal and paternal alleles when they're swapped between chromosomes
43
What is independent segregation
The random lining up of homologous pairs
44
How is the possible chromosomes number found
2^n | n = number of homologous pairs
45
Variety further increased through independent segregation, how can this be calculated
(2^n)^2
46
What is genetic diversity
Total number of different alleles in a population | Same as gene pool
47
What is a gene pool
Wide variety of alleles in a population | same as genetic diversity
48
What occurs in natural selection
1. A species population will have a gene pool with variety of alleles 2. Random mutation of alleles within gene pool, may cause new alleles of gene 3. Some environments the mutation gives a competitive advantage 4. Better adapted, more likely to out compete others 5. Survive and reproduce passing on genes 6. Frequency of allele increases in population
49
What occurs in directional selection
In environmental changes, phenotypes best suited to new conditions most likely survive Individuals fall left/right of mean, posses phenotype more suited to new conditions more likely survive, breed Contribute more offspring, pass on alleles Mean will move in direction of these individuals Results in phenotypes at one extreme of population being selected, at other extreme being selected against
50
What occurs in stabilising selection
If environment remains stable, phenotypes closest to mean survive More likely to pass on alleles Individuals with extreme phenotypes less likely to pass on alleles Tends to eliminate extreme phenotypes, mean value stays same and standard deviation smaller

Biology (4 decks)

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