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Biology A level > 4.1 DNA, Genes And Chromosomes > Flashcards

4.1 DNA, Genes And Chromosomes Flashcards

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1
Q

What is a gene?

A

A sequences of bases that codes for a specific polypeptide and functional RNA

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2
Q

How many genes are there per one polypeptide?

A

1

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3
Q

What are the 2 functional RNA?

A

tRNA
rRNA

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4
Q

What is a locus?

A

The position in which the gene if found in DNA

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5
Q

What does a sequence of bases in DNA determine?

A

A sequence of amino acids in a polypeptide

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6
Q

What does homozygous mean?

A

Alleles are the same

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7
Q

What does heterozygous mean?

A

Alleles are different

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8
Q

How many alleles are there per gene?

A

2

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9
Q

What is an allele?

A

Various forms of a gene

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10
Q

Which type of cell DNA is found in mitochondria and chloroplasts?

A

Prokaryotic

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11
Q

What is the difference in shape of the two cell types DNA?

A

Pro = circular (loop)
Euk = linear (two ends)

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12
Q

In which type of cell is DNA shorter?

A

Prokaryotic

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13
Q

Which type of cell DNA has introns?

A

Eukaryotic

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14
Q

What are introns?

A

The non-coding regions of DNA
Tends to be two bases that repeat itself

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15
Q

What are Exons?

A

Coding regions of DNA

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16
Q

When are chromosomes visible?

A

When the cell is dividing

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17
Q

How is DNA packed into a chromosome?

A

DNA wraps around his tone proteins to form a nucleosome
This coils to form super coils which makes up the chromatids

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18
Q

How many chromosomes are present in a human cell?

A

46 chromosomes

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19
Q

What is a homologous pair?

A

2 chromosomes with the same genes in the same loci

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20
Q

What is bivalent?

A

A replicated homologous pair of chromosomes

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21
Q

What is a karyotype?

A

The number and type of chromosomes in a cell

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22
Q

What does haploid mean?

A

1 set of chromosomes - no homologous pairs

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23
Q

What does diploid mean?

A

2 sets of chromosomes

24
Q

What is the genetic code?

A

The sequence of bases in DNA

25
Q

How many genetic codes do no code for an amino acid?

A

3

26
Q

How many bases code for 1 amino acid?

A

3

27
Q

What are the 3 features of the genetic code?

A

It is a degenerate code
Non-overlapping
Universal

28
Q

What does degenerate code mean?

A

more than 1 codon codes for a single amino acid

29
Q

What does non-overlapping mean?

A

Each base is only read once in each triplet

30
Q

What does universal genetic code mean?

A

Each triplet code codes for the same amino acid in any organism

31
Q

What amino acid is at the start of every polypeptide chain?

A

Methionine

32
Q

What is a genome?

A

The complete set of genes in cell or organism

33
Q

What is a proteome.

A

The entire set of proteins that can be produced by the genome

34
Q

What are 3 consecutive bases called in DNA?

A

A triplet

35
Q

What are 3 consecutive bases called in mRNA?

A

Codon

36
Q

What are 3 consecutive bases called in tRNA?

A

Anticodon

37
Q

What is the role of mRNA?

A

Carries the genetic code from DNA to the cytoplasm for protein synthesis

38
Q

What is the shape of mRNA?

A

A relatively long polynucleotide

39
Q

How is mRNA formed from DNA?

A
  1. DNA strands separate by breaking H bonds
  2. one of the strands is used as a template
  3. complementary base pairs form
  4. nucleotides joined by RNA polymerase
  5. pre-mRNA is formed
  6. splicing to remove introns to form mRNA
40
Q

What does the sequence of codons determine in mRNA?

A

The sequence of amino acids brought to the ribosome by tRNA

41
Q

What is the function of rRNA?

A

Makes up the ribosomes made in the nucleolus

42
Q

What is tRNA structure and features?

A

Relatively small
Single- stranded helix which is folded into a clover leaf shape
Hydrogen bonds
Amino acid attachment site with the anticodon unfolded

43
Q

How is the amount of genes in a gamete different to a human cell?

A

Gamete has half as many chromosomes

44
Q

What is the advantage of DNA being a stable molecule?

A

So it is relatively unchanged and can be passed down through generations as the same molecule

45
Q

What is the advantage of mRNA being broken down relatively quickly?

A

It is used to make proteins so it would be wasteful to produce proteins constantly
The mRNA is broken down to be reused

46
Q

What protein is prokaryotic DNA associated with?

A

Histones

47
Q

Which sex chromosome looks straight?

A

X

48
Q

What is the sex chromosome make up for a male?

A

XY

49
Q

What is the sex chromosome make up for a female?

A

XX

50
Q

What are the two threads in the chromosome called?

A

Chromatids

51
Q

What forms the non-coding parts of the gene?

A

By several short sequences that are usually two bases that repeat themselves

52
Q

What is the function of a STOP codon?

A

Signals a halt to protein synthesis in the cell

53
Q

What is the centre of a chromosome called?

A

Centromere

54
Q

How do you separate strands of DNA?

A

DNA helicase

Breaks hydrogen bonds between base pairs/ AT and GC/complementary bases

55
Q

What is the role of single-stranded DNA fragments?

A

act as a template and determines the order of nucleotides

56
Q

What is the role of DNA nucleotides?

A

forms complementary pairs

Biology A level (28 decks)

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