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

Genetic Information, variation and relationships between organisms Flashcards

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AP® Biology flashcards Biology 101 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

A

Introns

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
Q

What does RNA polymerase do

A

Move along mRNA strand forming sugar phosphate backbone

26
Q

What happens when a stop code is reached

A

Transcription stops, strand pre-mRNA made

27
Q

What happens in splicing

A

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
Q

Why doesn’t splicing occur in prokaryotes

A

DNA gene sequence doesn’t contain introns

29
Q

What happens to the mRNA after being spliced

A

Leaves nucleus out nuclear lire

Translation - mRNA attaches to ribosome in cytoplasm, becomes attached to starting codon

30
Q

What is a tRNA molecule made of

A

Specific amino acid at top, anticodon (triplet codon) at bottom

31
Q

How does the tRNA molecule bind the the mRNA strand and where

A

Complementary base pairing of codons Dorothy anticodon-codon complex at ribosome

32
Q

Why is ATP used in translation

A

To form peptide bond between amino acids uses ATP which is hydrolysed to provide energy

33
Q

What happens to the tRNA when it is released from its specific amino acid at ribosome

A

Free to collect another amino acid at its amino acid binding site

34
Q

What happens when stop code reached

A

Polypeptide synthesis stops and last tRNA separates

Form tertiary structure - disulphide bonds, hydrogen bonds, ionic bonds

35
Q

What can cause gene mutations

A

Base deletion and base substitution

36
Q

Why does base substitution not always cause mutations

A

Degenerate code

37
Q

What is a mutagenic agent

A

Can increase rate of gene mutation

38
Q

What is meiosis

A

Cells division that makes four genetically different games

39
Q

What happens during meiosis

A
  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
Q

Why are sex cells haploid

A

So diploid number restored at fertilisation

41
Q

How does meiosis cause genetic variation

A

Crossing over and independent segregation

42
Q

What is crossing over

A

New combinations of maternal and paternal alleles when they’re swapped between chromosomes

43
Q

What is independent segregation

A

The random lining up of homologous pairs

44
Q

How is the possible chromosomes number found

A

2^n

n = number of homologous pairs

45
Q

Variety further increased through independent segregation, how can this be calculated

A

(2^n)^2

46
Q

What is genetic diversity

A

Total number of different alleles in a population

Same as gene pool

47
Q

What is a gene pool

A

Wide variety of alleles in a population

same as genetic diversity

48
Q

What occurs in natural selection

A
  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
Q

What occurs in directional selection

A

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
Q

What occurs in stabilising selection

A

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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