3.4.1 DNA, Genes + Chromosomes Flashcards

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1
Q

How many chromosomes do humans have

A

46 chromosomes (23 pairs)

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2
Q

What are DNA molecules like in prokaryotic cells

A

Short,circular and not associated with proteins

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3
Q

What are DNA molecules like in the nucleus of eukaryotic cells

A

Very long,linear and associated with histone proteins

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4
Q

What proteins are dna molecule sin a eukaryote associated with

A

Histones

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5
Q

What does a dna molecule and its associated proteins form

A

A chromosome

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6
Q

In eukaryotic cells, what other 2 organelles contain dna

What’s it like

A

Mitochondria + chloroplasts

Short,circular and not associated with proteins (like prokaryotic dna)

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7
Q

What are homologous chromosomes

A

Chromosome pairs where each chromosome is alike and have genes for the same characteristic at corresponding loci (positions)

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8
Q

What are alleles

A

Genes which occur at the same position (loci) on a pair of homologous chromosomes

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9
Q

What’s a gene

What does it code for

A

A short length of dna that codes for :

  • amino acid sequence of a polypeptide
  • a functional RNA (including ribosomal RNA + tRNAs)
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10
Q

What does a gene occupy on a particular dna molecule

A

A fixed position called a locus

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11
Q

What does each triplet on a gene code for

A

Amino acid

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12
Q

What does the degenerate code mean

A

Some amino acids have more than 1 codon

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13
Q

What does it mean when the code is non-overlapping

A

Each base is part of 1 codon sequence of triplets/bases that code for a protein

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14
Q

What does it mean if the code is universal

A

3 base triplets code for amino acid in every species +cell from simple to complex

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15
Q

How many codons code for 20 amino acids

A

64

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16
Q

Why is the genetic code degenerate

A

As many amino acids can be coded for by several different codons (64 codons code for 20 amino acids)

17
Q

What’s the genome

A

Complete set of genes in a cell

18
Q

What’s the proteome

A

Full range of proteins a cell can produce

19
Q

What’s RNA

A

A nucleic acid like DNA but with differences

20
Q

4 differences RNA has to DNA

A
  • has ribose sugar instead of deoxyribose
  • has the base uracil instead of thymine
  • usually single stranded
  • usually shorter than dna
21
Q

What can rna do like proteins

A

Fold into 3D

22
Q

What does mRNA do

A

Carries the message that codes for a particular proteins from the nucleus (where DNA master copy is) to the cytoplasm (where proteins are synthesised in ribosomes)

23
Q

What’s mRNA like

A

Single stranded

Just long enough to contain 1 gene only

24
Q

What happens to mRNA shortly after it’s used

A

It’s degraded - has a short lifetime

25
Q

Why would a cell have a higher concentration of mRNA

A

If it’s doing more protein synthesis

26
Q

What does rRNA with proteins form

A

Ribosomes

27
Q

What’s rRNA

A

Ribosomal rna

28
Q

What are ribosomes the site of

A

mRNA translation and protein synthesis

29
Q

What are ribosomes made up of

A

2 subunits, small and large

30
Q

What’s rRNA codes for by

A

Numerous genes in many different chromosomes

31
Q

What 2 places are ribosomes

A

Cytoplasm

RER

32
Q

What do free ribosomes in the cytoplasm make protein for

A

Cell use

33
Q

What do ribosomes attached to the RER make proteins for

A

Export

34
Q

Describe the genetic code (3)

A

Universal
Non-overlapping
Degenerate

35
Q

What’s a triplet

A

Sequence of 3 DNA bases

36
Q

Within a gene what the sequences that actually code for amino acid sequences called

A

Exons

37
Q

What are exons separated by within the gene

A

One/more non-coding sequences called introns