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GCSE Biology AQA > B13 - Reproduction 2️⃣✅ > Flashcards

B13 - Reproduction 2️⃣✅ Flashcards

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1
Q

What is a gamete?

A

A sex cell

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2
Q

What are the 2 types of human gametes>?

A

sperm & egg cells

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3
Q

What are the 2 types of plant gametes?

A

pollen & egg cells

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4
Q

What is sexual reproduction?

A

Sexual reproduction involves the joining of two sex cells, or gametes during fertilisation. Organisms produced by sexual reproduction have two parents and are genetically similar to both but not identical to either - offspring are varied

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5
Q

What is asexual reproduction?

A

Asexual reproduction only involves one parent so there is no joining of sex cells during fertilisation. Organisms produced by asexual reproduction are genetically identical to each other and their parent. They are clones

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6
Q

In what type of reproduction are gametes made?

A

Sexual

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7
Q

In what type of reproduction does the fusion of cells occur?

A

Sexual

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8
Q

In what type of reproduction are offspring varied?

A

Sexual

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9
Q

In what type of reproduction are offspring genetically identical?

A

Asexual

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10
Q

In what type of reproduction can evolution/ mutation occur?

A

Sexual

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11
Q

What type of reproduction uses more energy?

A

Sexual

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12
Q

What is a diploid cell?

A

Contain 2 sets of chromosomes (one from each parent)

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13
Q

What is a haploid cell?

A

Contain 1 set of chromosomes (to fuse to make 2 eventually in fertilisation)

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14
Q

What type of reproduction involves mitosis and how?

A

Asexual
Mitosis creates genetically identical cells (offspring) and therefore produces clones - same as asexual reproduction, creates clones of itself with no variation

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15
Q

What type of reproduction involves meiosis and how?

A

Sexual
Creates gametes that are varied to increase genetic variation in offspring - ideal for sexual reproduction as its also creating varied offspring

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16
Q

How many cell divisions occur in mitosis & meiosis?

A

Meiosis: 2
Mitosis: 1

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17
Q

How many daughter cells are produced in mitosis & meiosis?

A

Meiosis: 4
Mitosis: 2

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18
Q

In what areas of the body do mitosis & meiosis occur?

A

Meiosis: testes and ovaries only
Mitosis: everywhere else

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19
Q

What is the purpose of meiosis?

A

To produce gametes that increase genetic variation in offspring

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20
Q

What is the number of chromosomes after cell division in meiosis?

A

23

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21
Q

Why are there only 23 single chromosomes in gametes?

A

Because 1 gamete from each parent will fuse in fertilisation and the 23 chromosomes from each gamete will fuse to create 46 total chromosomes and 23 pairs to create a embryo with genetic infromation from both parents

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22
Q

Where within the nucleus is DNA found?

A

Chromosomes

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23
Q

What is a genome?

A

The genome of an organism is the entire genetic material of that
organism.

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24
Q

How does meiosis work?

A
  1. DNA replicated
  2. Matching pairs line up next to eachother in centre of cell and undergo a gene swap
  3. Cells divide once
  4. Pair inside cell splits therefore dividing a second time
  5. Overall leaving 4 gamets genetically different from eachother
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25
Q

What is the monomer DNA is made up of?

A

Nucleotide

26
Q

What 3 things make up a Nucleotide??

A
  • phosphates
  • deoxyribose sugar
  • DNA base
27
Q

What is the structure of DNA?

A

A double helix pattern containing long chains of nucleotides

28
Q

What are the letters of the 4 DNA bases and what are there pairs?

A
  • A
  • T
  • G
  • C
  • A - T
  • G - C
29
Q

What is an allele?

A

An alternative form of a gene

30
Q

What does it mean when something is dominant?

A

An allele that is always expressed even if only one copy is present

31
Q

What does it mean when something is recessive?

A

An allele that is only expressed if two copies of it are present

32
Q

What does homozygous mean?

A

A genotype that has two of the same alleles. Either two dominant alleles, or two recessive alleles (homo - the same)

33
Q

What does heterozygous mean?

A

A genotype that has to different alleles - one dominant and one recessive

34
Q

What does genotype mean?

A

The combination of alleles that make up the gene e.g. BB, bb, Bb

35
Q

What does phenotype mean?

A

The characteristic expressed because of the combination of alleles

36
Q

What are the benifits of understanding the human genome?

A
  • Discovering genes linked to different types of disease
  • Understanding and treatement of inherited disorders
  • Use in tracing human migration patterns from the past
37
Q

How are amino acids produced in terms of soully DNA bases?

A

The triplet code - a sequence of three bases is the code for a specific amino acid. The order of the 3 bases controls the order in which amino acids are assembled to produced a particular protein

38
Q

How does protein synthesis work?

(7 steps)

A
  1. double helix DNA is ‘unzipped’ to expose genetic instructions for specific protein
  2. TRANSCRIPTION - single strand of template DNA is made via transcription. (A copy of the gene DNA base order but corresponding not direct copy e.g. A-T-C-G would be T-A-G-C on template)
  3. Single stranded template DNA is small & mobile so is able to exit the nucleus through the nuclear pores so it can get to ribosomes in cytoplasm
  4. Template strand attaches to ribsome so the triplet DNA code can be used for amino acid production
  5. TRANSLATION - amino acid carrier brings corresponding bases with ones inside ribosome into place using DNA base pair rules
  6. The two adjacent amino acids are bonded together to make an amino acid chain using energy from respiration
  7. Amino acid chain then folds up into complex 3d shape (a functional protein) enabling protein to do there jobs as enzymes etc
39
Q

What is the second main stage of protein synthesis called and where does it take place?

A

Translation, in ribosomes

40
Q

What is the first main stage of protein synthesis called and where does it take place?

A

Transcription, in nucleus

41
Q

What happens if the triplet code is not aligened correctly during translation?

A

There would be a knock-on affect and all aminio acid chains produced would be faulty/ incorrect, leading amnio acids to fold up into incorrect shapes

42
Q

What is an altered protein?

A

When a mutation causes a change in the amino acid and therefore the amnio acids fold up into a different shape. For example an enzyme ends up having a faulty active site and cant fit with substrate and a structural protein would loose its strength

43
Q

What are non-coding parts of DNA?

A

Non-coding parts of DNA can switch genes on and off, so variations in these areas of DNA can end up changing how genes are expressed and therefore sometimes the phenotype of an organism

44
Q

What are the 2 possible outcomes of mutation?

A
  • Weaker structural Proteins and enzymes with faulty active sites where substrate cant fit
  • Stronger strucutrual protien and enzymes are more efficient
45
Q

What is a gene expression?

A

Where specific genes are activated to produce a required protein

46
Q

Are mutations rare or common?

A

Mutations are common and usually dont alter the protein or only alter it slightlty so everything remainds the same. The more rarer mutation is when a protein is altered so that it becomes an altered protein and changes in function/ expression and therefore phenotype

47
Q

Name 2 inhertited disorders and which one is recessive/ dominant?

A

Cystic fibrosis - recessive
Polydactyly - dominant

48
Q

What is cystic fibrosis?

A

A disorder of the cell membranes that causes a thick sticky mucus in lungs

49
Q

What is polydactyly?

A

When a person is born with extra fingers or toes

50
Q

A: affected by disorder a: unaffected by disorder

If an inhertied disorder was dominant and the person had the genotype of (Aa), would they have the disorder and why/ why not if so?

A

Given their genotype (Aa), the person would have the disorder as it is dominant, meaning that only 1 allele is required for the gene to be expressed

51
Q

A: affected by disorder a: unaffected by disorder

If an inhertied disorder was recessive and the person had the genotype of (Aa), would they have the disorder and why/why not if so?

A

Given their genotype (Aa), the person would not thave the disorder as it is a recessive disorder, meaning that due to it being recessive, 2 alleles would have to be present for the gene to be expressed. Therefore as only one is present (a), the person would not have the disorder, but would be a carrier for it.

52
Q

A: affected by disorder a: unaffected by disorder

If an inhertied disorder was recessive and the person had the genotype of (aa), would they have the disorder and why/ why not if so?

A

Given their genotype (aa), the person would have the disorder as it is a recessive disorder and they have 2 recessive alleles present, meaning that the gene would be expressed, therefore causing the person to have the disorder

53
Q

What is a carrier?

A

A person who has one recessive allele in a genotype that isnt expressed in them, but can lead to being expressed in offspring

54
Q

What are the female sex chromosomes?

A

(XX)

55
Q

What are the male sex chromosomes?

A

(XY)

56
Q

How can embryos be screened for genetic disorders?

A

Through IVF, prior to implantation a cell can be removed from each embryo and screened for specific genes that correlate to inherited/ genetic disorders to check before impregnanting.
There are also other methods such as amniocentesis and chronic villus sampling.

57
Q

What is amniocentesis? When is it carried out? What methods?

A
  • Taking some of the fluid from around the foetus as it contains foetal cells and screening them for genetic/ inhertited disorders
  • Carried out between 15-16 weeks of pregnancy
  • Transabdominal method (stomach)
58
Q

What is Chronic villus sampling? When is it carried out? What methods?

A
  • Taking sample of tissue from the developing placenta which includes foetal cells which can be used for screening for genetic/ inhertied disorders
  • Carried out quite early at 10-12 weeks of pregnancy
  • Transabdomnial method (stomach) or Transcervical method (cervix)
59
Q

What are arguments against genetic embryo screening?

A
  • implies people with genetic problems are undesirable - prejudice
  • may make others want to ‘choose’ the most ‘desirable’ embryo e.g blue eyes, intelligent etc
  • Screening is very expensive
60
Q

What are arguments for genetic embryo screening?

A
  • Will help parents with inherited disorders from passing it on to there children - preventing further suffering
  • Treating the disorders can sometimes rival the costs of the screening in the first place
  • There are laws in place to prevent it from going to far - at the moment parents are not allowed to choose the sex of there baby (unless for health reasons)

GCSE Biology AQA (16 decks)

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