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Biology gcse > ⭐️SB3 - Genetics > Flashcards

⭐️SB3 - Genetics Flashcards

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1
Q

What’s asexual reproduction?

A

Where some organisms can reproduce without fertilisation producing clones

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2
Q

In animals, which types reproduce in what ways?

A

Invertebrates - asexually

Vertebrates - mainly sexually

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3
Q

Give the definition of sexual reproduction

A

Combines characteristics of both parents so the offspring are different to each other

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4
Q

Give two advantages of sexual reproduction

A
  • offspring can adapt if they move to new environmental conditions
  • causes variation among offspring so the species is more likely to survive a disease or new pest e.c.t
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5
Q

What are the advantages of asexual reproduction?

A
  • Much faster than sexual reproduction as there’s no need to find a mate
  • requires less energy to reproduce
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6
Q

State the main difference between the offspring produced in sexual reproduction vs asexual reproduction

A

Sexual reproduction produces offspring with variation but asexually reproduced offspring are clones to the parent

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7
Q

Where doesn’t meiosis take place?

A

In asexual reproduction

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8
Q

What are gametes?

A

Sex cells

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9
Q

What’s a zygote?

A

A single fertilised egg cell

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10
Q

What process causes a zygote to form a ball of cells?

A

Mitosis

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11
Q

What us DNA?

A

The code in a molecule that are the instructions for an organism

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12
Q

Where is a molecule of DNA found?

A

In the Chromosome of a cell

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13
Q

What is the genome?

A

The DNA of an organism, most cells contain a complete copy of a genome

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14
Q

What are genes?

A

Sections of DNA molecules that contain a code for making proteins

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15
Q

What controls the order of amino acids in polymers?

A

Genes, humans have around 20,000

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16
Q

How many chromosomes does a diploid and a haploid cell have?

A

Diploid cell has 46, haploid cell has 23

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17
Q

What kind of cells are gametes?

A

Haploid cell’s

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18
Q

Why do brothers and sisters look similar but aren’t identical

A

As each human chromosome in a pair contains different versions of the same gene making them genetically different

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19
Q

How are proteins polymers?

A

They are made by linking different amino acids together in a chain

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20
Q

What process is used to produce gametes?

A

Meiosis

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21
Q

What step happens before meiosis?

A

Interphase

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22
Q

What kind of cell starts off in meiosis?

A

A diploid gamete making cell

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23
Q

What are the steps of meiosis?

A
  1. the chromosomes of the diploid cell replicate
  2. The cell divides into two diploid cells
  3. These new cells each divide again
  4. The four daughter cells are haploid as they have a copy of one chromosome from each pair
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24
Q

What are chromosomes made of?

A

Molecules of dna tightly coiled and packaged up with proteins

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25
Q

What is the shape of a DNA molecule?

A

Two strands forming a double helix structure?

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26
Q

What joins the two strands in DNA?

A

Pairs of bases

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27
Q

What are the base pairs?

A

Adenine - thymine

Cytosine - guanine

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28
Q

What are matching bases?

A

Complimentary base pairs

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29
Q

What’s a nucleotide?

A

The base attached to a sugar attached to a phosphate group in a dna molecule

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30
Q

What holds bases together?

A

Hydrogen bonds

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31
Q

Draw a labelled diagram of a dna molecule including the nucleotide

A

Check the notepad to see if it’s correct

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32
Q

How do the base pairs have a hydrogen bond between them?

A

As the slightly negative charged part on one of the base pairs attracts another positively charged part of a base pair forming a weak force of attraction being a hydrogen Bond

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33
Q

Describe the backbone of a dna strand

A

The sugar and phosphate group

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34
Q

Why do bass pairs pair specifically?

A

Because C-G form 3 hydrogen bonds between them but A-T form 2 hydrogen bonds between them

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35
Q

What’s important about the order of bases in a gene?

A

As they contain the coded instructions for the protein

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36
Q

What’s starch a polymer of?

A

Glucose

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37
Q

What’s cellulose a polymer of?

A

Glucose

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38
Q

What’s the type of sugar in a nucleotide?

A

Deoxyribose sugar

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39
Q

Each gene codes for a specific sequence of…

A

Amino acids to make a specific protein

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40
Q

What are the steps in transcription?

A
  1. RNA polymerase attaches to the non coding part of the DNA
  2. This causes the enzyme to separate into two strands
  3. The RNA polymerase moves along the DNA strand adding complimentary RNA nucleotides
  4. The nucleotides link to form a strand of RNA
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41
Q

What’s the first and second stage of protein synthesis?

A

Transcription .1

Translation .2

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42
Q

What’s the difference between DNA and RNA

A

In RNA instead of thymine, uracil is used

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43
Q

What’s RNA polymerase?

A

An enzyme responsible for creating mRNA in transcription

44
Q

What is a non-coding strand of DNA?

A

A region of DNA that doesn’t contain a code for a protein

45
Q

Where does translation occur?

A

In the cytoplasm

46
Q

Where does transcription occur?

A

In the nucleus

47
Q

What are the steps in translation?

A
  1. mRNA leaves the nucleus through nuclear pores into the cytoplasm
  2. The mRNA strand attaches to a ribosome in the cytoplasm
  3. The ribosome moves along the mRNA strand a codon at a time where a molecule of tRNA lines up
  4. Each tRNA carries a specific amino acid and they join as the ribosome moves along forming a polypeptide
48
Q

What’s a polypeptide?

A

A chain of amino acids

49
Q

What happens at the end of protein synthesis when the polypeptide forms?

A

It folds to form a protein with a specific shape

50
Q

What are ribosomes made of?

A

RNA and protein

51
Q

What’s a mutation?

A

A change in the genetic bases of a gene. The same as a genetic variant

52
Q

When can mutations happen?

A

When DNA isn’t copied correctly or by environmental factors

53
Q

What can mutations cause to an organism?

A

A change in their phenotype (the way they look)

54
Q

What are alleles and what causes them?

A

They are different forms of the same gene and are caused by mutations

55
Q

How many polypeptides does haemoglobin contain?

A

Four of the kinds alpha and beta

56
Q

What do the haemoglobin polypeptides form?

A

Globular proteins which carry oxygen

57
Q

What causes sickle cell disease?

A

A base change causing a different amino acid so the haemoglobin polypeptide folds incorrectly

58
Q

why do mutations not happen all the time in a base change?

A

As codons can sometimes encode for the same amino acid in which case the folding of the protein is un affected

59
Q

What is meant by the term genetic disorder?

A

A disorder caused by faulty alleles

60
Q

Only when can mutations effect protein synthesis?

A

If they take place in the non coding section of DNA

61
Q

What kind of mutation causes B-thalassemia?

A

A mutation in the non coding region of dna so rna polymerase doesn’t bind well and so transcription is reduced

62
Q

When may too much mRNA be produced?

A

When there is a mutation in the non coding section of dna that causes RNA polymerase to bind better

63
Q

What does variation mean?

A

Differences in the characteristics in a group of the same organism

64
Q

What did scientists used to believe about the characteristics among offspring

A

That they were blended instead of inherited

65
Q

What conclusion did mendel’s experiments lead him to make?

A

Characteristics are not blended during inheritence but instead we’re determined by inherited units that don’t change when passed on to descendants

66
Q

How did Mendel’s work lead to the discovery of recessive alleles?

A

As he noticed some characteristics were masked and then reappeared in later generations

67
Q

How did scientists begin to notice mendels work?

A

When they noticed his units behaved similarly to chromosomes in cell division and the units were then renamed genes

68
Q

Why did Mendel use pea plants?

A

They have multiple variable traits that are clearly visible like seed colour, pod colour and shape

69
Q

Why may each copy of a gene be a different allele?

A

Because as there two copies of every chromosome in a body cell nucleus and so each body cell contains two copies of the same gene

70
Q

What gives us genetic variation?

A

The different combination of alleles

71
Q

What does it mean if an organism is homozygous?

A

Both alleles for one gene are the same

72
Q

What does it mean if an organism is heterozygous?

A

The alleles are different to each other

73
Q

When is a recessive characteristic seen?

A

If both alleles are recessive

74
Q

How do you represent dominant and recessive alleles?

A

Dominant are capitals, recessive are lowercase. Dominant is always written before the recessive one

75
Q

What is a genotype?

A

The alleles in an organism

76
Q

What’s a phenotype?

A

What an organism looks like

77
Q

What is monohybrid inheritance?

A

The inheritance of one gene e.g. TT or tt

78
Q

What determines your sex? What are they?

A

Sex chromosomes. females have two X chromosomes and males have two Y chromosomes

79
Q

What is cystic fibrosis? What problems does it cause?

A

It’s a genetic disorder caused by the recessive allele where people have issues with their lungs and digestive system

80
Q

Give the likely hold of offspring having cystic fibrosis of the parents are heterozygous for the CF gene

A

25% likely

81
Q

What allele causes polydactyly?

A

The dominant allele

82
Q

What are the four blood groups?

A

A, B, AB and O

83
Q

What determines your ‘marker molecules’? What are they?

A

Your blood group, these are A, B and O

84
Q

Describe the genes responsible for the markers in the ABO system. What’s recessive to what?

A

They are alleles written as I^A I^B and I^O. Everyone has two copies of the same gene and I^O is recessive to both I^A and I^B.

85
Q

What does co-dominant alleles mean? Give an example.

A

Where both alleles for a gene affect the phenotype. For example a person with the genotype I^A I^B shows the effect of both alleles and has the blood group AB

86
Q

A person has the blood group AB. What’s their genotype?

A

I^A I^B

87
Q

What is the meaning of sex-linked genetic disorder?

A

Disorders that show a different pattern of inheritance in men and women are called sex linked genetic disorders

88
Q

What are the 6 possible genotypes for blood?

A

I^A I^B, I^O I^O, I^A I^A, I^B I^B,

I^B I^O, I^A I^O

89
Q

Why will a man only have one allele for some genes on the X chromosome?

A

Because a human Y sex chromosome is missing some of the genes found on the X sex chromosome.

90
Q

Why are men more likely to develop sex linked genetic disorders?

A

As if the allele for an X chromosome gene causes a genetic disorder then a man will develop it because there is no allele on the Y chromosome to potentially cancel it out

91
Q

State 2 diseases caused by a sex linked genetic disorder

A

Red green colour blindness and haemophilia

92
Q

Why can red green colour blindness happen?

A

Due to cone cells in the retina not working properly

93
Q

What is a mutation?

A

A change that creates a new allele.

94
Q

When do mutations happen? Why?

A

When there is a mistake in copying DNA during cell division. This can be because of the DNA being damaged due to radiation or certain substance

95
Q

Explain why a mutation doesn’t always produce a change in a characteristic

A

Because mutations can occur in different parts of a gene and so don’t always largely effect the protein produced or don’t change the protein at all

96
Q

Give two benefits of mapping someone’s genome

A
  • to indicate their risk of developing diseases caused by different alleles
  • to identify which medicines are best to treat someone’s illness as alleles can affect how medicine works in the body
97
Q

What has the human genome project shown?

A

Their are variations between people but over 99% of DNA bases in different people are the same

98
Q

Why should you keep in mind the alleles of a patient in clopidogrel?

A

As some have alleles that mean the drug doesn’t protect them against blood clots if they’re at risk of a heat attack or stroke

99
Q

What causes genetic variation?

A

Different alleles inherited during sexual reproduction

100
Q

What is environmental variation?

A

Characteristics affected by the surroundings

101
Q

What are acquired characteristics?

A

A characteristic of an organism that can change during its life due to a change in the environment e.g. loss of a limb

102
Q

What are the two types of variation and their meanings?

A

Discontinuous variation=data can only take a limited set of values

Continuous variation=data can be any value in a range

103
Q

How do you know if a frequency bar chart is showing continuous or discontinuous variation?

A

As continuous variation doesn’t have any gaps between the bars but discontinuous variation does have gaps between the bars

104
Q

What does continuous data form on a graph usually?

A

A bell shaped curve

105
Q

What is a normal distribution?

A

The bell shaped curbs formed by continuous data

106
Q

What were the three laws of inheritance that Mendel came up with?

A
  • Each gamete only receives one hereditary unit for a characteristic
  • hereditary factors are passed on unchanged from parent to offspring and there’s one factor per parent
  • same versions of a factor are more powerful than others and always have an affect on the expression of a characteristic

Biology gcse (32 decks)

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