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Edexcel Gcse Biology > Paper 1 - Topic 3, Genetics > Flashcards

Paper 1 - Topic 3, Genetics Flashcards

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1
Q

What type of cells does sexual reproduction produce

A

Genetically different cells

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2
Q

What is produced in sexual reproduction

A

Gametes, sperm and egg cells

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3
Q

What do gametes contain

A

Half the number of chromosomes of normal cells - haploid cells

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4
Q

What happens at fertilisation

A

A male gamete fuses with a female gamete to produce a fertilised egg

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5
Q

What is a fertilised egg called

A

A zygote

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6
Q

How does a zygote develop into an embryo

A

Cell division by mitosis

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7
Q

How many chromosomes does a human cell contain

A

46

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8
Q

Where are the male gametes found in flowers

A

The pollen

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9
Q

Where are the female gametes found in flowers

A

In the ovaries at the bottom of a stigma

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10
Q

How is meiosis different to mitosis

A

Meiosis produces genetically different cells, meiosis only happens in the reproductive organs

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11
Q

Describe division 1 of meiosis

A
  1. It duplicates its DNA, one arm of each X-chromosome is an exact copy of the other arm
  2. The chromosomes then line up in centre of cell, one chromosome in each pair came from the mother and one from the father
  3. The pairs are pulled apart so each new cell has one copy of each chromosome, some of the mothers and father’s chromosomes in each new cell
  4. Each new cell has mixture of mothers and fathers chromosomes, mixing up genes creates genetic variation in offspring
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12
Q

Describe division 2 in meiosis

A
  1. The chromosomes line up again in centre of cell, the arms of the chromosomes are pulled apart
  2. You then get four haploid daughter cells, these are gametes, each gamete has a single set of chromosomes, the gametes are genetically different
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13
Q

What happens if something reproduces asexually

A
  • divide by mitosis
  • results in two diploid daughter cells
  • they are genetically identical to each other and the parent
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14
Q

What happens if something reproduces sexually

A
  • meiosis
  • produces genetically different haploid gametes which fuse to form a diploid cell at fertilisation
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15
Q

What are the advantages of asexual reproduction

A
  • can produce lots of offspring very quickly because the reproductive cycle is so quick
  • only one parent is needed - organisms can reproduce whenever conditions are favourable without having to wait for a mate
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16
Q

What are disadvantages of asexual reproduction

A
  • no genetic variation so if environment changes and conditions become unfavourable, whole population may be affected
17
Q

What are the advantages of sexual reproduction

A
  • creates genetic variation within population so individuals have different characteristics and if environment changes its more likely some individuals will survive the change
18
Q

What are the disadvantages of sexual reproduction

A
  • takes more time and energy, so less offspring are created in an organisms lifetime (need to attract mates which takes time and energy
  • two parents are need so if individuals are isolated it can be a problem
19
Q

What do nucleotides consist of

A

A sugar, a phosphate and one base

20
Q

What does the sugar and phosphate create

A

The backbone

21
Q

What are DNA strands

A

Polymers made up of lots of repeating units called nucleotides

22
Q

What are the four bases called

A

Adenine
Thymine
Cytosine
Guanine

23
Q

What are the complementary base pairs joined together by

A

Weak hydrogen bonds

24
Q

Where are chromosomes found

A

In the nucleus of a eukaryotic cell

25
Q

What is a gene

A

A section of DNA on a chromosome that codes for a particular protein

26
Q

How do you extract DNA from fruit cells

A
  1. Mash strawberries and put in beaker containing a solution of detergent and salt and mix
  2. Filter mixture to get the froth and big insoluble cells out
  3. Add ice cold alcohol to filtered mixture
  4. DNA will start to come out solution as not soluble in cold alcohol, appears as stringy white precipitate
27
Q

What will the detergent salt solution do in the DNA extraction from fruit cells experiment

A

Detergent: break down the cell membranes to release DNA
Salt: make DNA stick together

28
Q

What are proteins made up of

A

Amino acids

29
Q

What do the order of bases in a gene determine

A

The order of amino acids in a protein

30
Q

How is each amino acid coded

A

By a sequence of three bases in a gene

31
Q

What is a mutation

A

A rare ,random change to an organisms DNA base sequence that can be inherited

32
Q

What happens if a mutation happens in a gene

A

Produces a genetic variant

33
Q

Where are proteins made

A

In the cell cytoplasm by ribosomes

34
Q

What is mRNA

A

Messenger RNA, a polymer of nucleotides which is short and single stranded and uses Uracil instead of Thymine

35
Q

What is RNA polymerase

A

The enzyme involved in joining together RNA nucleotides to make mRNA

36
Q

How does transcription work

A
  1. RNA polymerase binds to a region of non-coding DNA in front of a gene
  2. The two DNA strands unzip and the RNA polymerase moves along one of the strands of DNA
  3. It uses the coding DNA in the gene as a template to make the mRNA, base pairing between the DNA and RNA ensures that the mRNA is complementary to the gene
  4. Once made the mRNA moves out of the nucleus and joins with a ribosome
37
Q

How does translation work

A
  1. Amino acids are brought to ribosomes by another RNA molecule called transfer RNA (tRNA)
  2. The order in which amino acids are brought to ribosomes matches the order of base triplets in the mRNA (base triplets called codons)
  3. Part of the tRNA structure in an anticodon which is complementary to the codon for the amino acid, the paring of the codon and anti-codon make sure amino acids are brought to ribosome in correct order
  4. The amino acids are joined together by ribosome which makes polypeptide

Edexcel Gcse Biology (9 decks)

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