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Biology- Porteous > 3.4.1 DNA, Genes and Chromosomes > Flashcards

3.4.1 DNA, Genes and Chromosomes Flashcards

1
Q

Describe DNA molecules in prokaryotic cells?

A

Short
Circular
Not associated with proteins

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2
Q

How does protein synthesis differ in prokaryotic and eukaryotic cells?

A

Transcription occurs in the nucleus in a eukaryotes; transcription occurs in the cytoplasm of a prokaryote
Translation occurs in the cytoplasm of eukaryotes and prokaryotes

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3
Q

Where is DNA found in prokaryotic cells?

A

Loose in the cytoplasm

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4
Q

Where is DNA found in eukaryotic cells?

A

In a membrane bound nucleus

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5
Q

In what form is the DNA in a prokaryotic and eukaryotic cell?

A

Prokaryotic- a single loop (with plasmids)

Eukaryotic- linear chromosomes

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6
Q

Is the DNA is prokaryotic and eukaryotic cells associated with proteins?

A

Prokaryotic- no (not a chromosome)

Eukaryotic- yes, wrapped around histones

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7
Q

What is the length of the DNA molecules in a prokaryote and eukaryotes?

A

Prokaryote- shorter

Eukaryote- longer

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8
Q

Where is DNA found in eukaryotic cells?

A

Nucleus
Mitochondria
Chloroplasts

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9
Q

How is DNA thought to have got into mitochondria and chloroplasts?

A

Endosymbiotic theory

Mitochondria and chloroplasts were once free living prokaryotes that were engulfed by a cell

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10
Q

Define chromosome.

A

Thread like structure found in the nucleus of eukaryotic cells
Consists of a single molecule of DNA
Highly wound around protein molecules called chromatin

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11
Q

What is a gene?

A

A section of DNA that codes for the amino acid sequence of one polypeptide

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12
Q

What is a locus?

A

The position on a particular chromosome where you find a gene

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13
Q

What is a homologous pair?

A

Chromosome pairs
One from each parent
Similar in length, gene position and centromere location

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14
Q

How many pairs of chromosomes does a human have?

A

23

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15
Q

What is an allele?

A

The different forms a gene can take

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16
Q

Define diploid.

A

A cell that contains two sets of chromosomes

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17
Q

What is a diploid number?

A

The number of chromosomes in a cell

Abbreviated to 2n (where n is the number of chromosomes)

18
Q

Define homozygous.

A

Where both alleles for a gene are the same

19
Q

Define heterozygous.

A

Where the alleles for a gene are different

20
Q

What does it mean if a cell is haploid?

A

Contains one complete set of chromosomes

21
Q

Give an example of a haploid cell?

A

Gametes

22
Q

When are haploid cells produced?

A

Meiosis

23
Q

What is the haploid number?

A

Number of chromosomes within the cell that is the set

24
Q

Define genome.

A

The full set of genes in a cell

25
Q

Define proteome.

A

The full range of proteins coded for by the genes

26
Q

Define karyotype.

A

The number and appearance of chromosomes in the nucleus of a eukaryotic cell

27
Q

Why isn’t DNA stored in the nucleus of a prokaryotic cell?

A

They have no nucleus!

28
Q

What is the purpose for the cooling of DNA in a chromosome?

A

So it is easy to separate/ unravel DNA without damaging it

For DNA replication

29
Q

Describe the structure of a chromosome.

A

A DNA double helix strand forms a chromatin fibre
This wraps around histone proteins
Histone proteins coil to make a chromatin fibre
These form loops
Loops form rosettes
These coil together
One chromatid is 10 coils long

30
Q

Define exon.

A

Sequences of bases in a gene that code for a sequence of a amino acids in a protein

31
Q

Define intron.

A

Non-coding DNA which can be found between genes in multiple repeats or within genes

32
Q

Why is DNA a ‘universal code’?

A

DNA is used in virtually all organisms as the material of inheritance

33
Q

What is a codon?

A

The sequence of three bases that codes for one amino acid

34
Q

What is degenerate code?

A

Amino acids are coded for by more than 1 codon

35
Q

What makes DNA ‘non-overlapping’?

A

Each base in the sequence is read only once so the code is non-overlapping

36
Q

Why are three bases needed to core for each amino acid?

A

There are 4 bases
If one base coded for one amino acid there would only be 4 possibilities
If they were in pairs there would only be 16 possibilities
We need 20 different codes
With 3 bases there are 64 possible combinations

37
Q

What is an advantage to a cell of having degenerate code?

A

If there is a substitution mutation in the third base of a codon, the impact will be small on the amino acid made
(eg GGA and GGG codes for the same thing)

38
Q

Which bases are involved in the triplet code table?

A

ATGC

39
Q

Ow many amino acids would be coded for from AAACACTTGGTC?

A

4

40
Q

What do polypeptides combine to produce?

A

Proteins

Biology- Porteous (14 decks)

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