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Biology Paper 2 > B13 Reproduction > Flashcards

B13 Reproduction Flashcards

1
Q

How many chromosomes would you find in a human skin cell?

A

46

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2
Q

What does mitosis result in the formation of?

A

2 genetically identical daughter cells

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3
Q

What is the difference between a gene and a chromosome?

A

Chromosomes contain many genes. A gene is a small section of DNA that codes for a specific protein/characteristic

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4
Q

What is the main difference between prokaryotic and eukaryotic cells?

A

Eukaryotic cells have a nucleus, prokaryotic cells do not

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5
Q

By which process to bacterial cells divide?

A

Binary fission

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6
Q

What is asexual reproduction?

A

Involves only one individual and the offspring is identical to the parent. There is no fusion of gametes or mixing of genetic information

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7
Q

What is sexual reproduction?

A

Involves the fusion (joining) of male and female gametes producing genetic variation in the offspring

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8
Q

what is meiosis?

A

2 stage process of cell division that reduces the number of chromosomes of daughter cells. Involved in making gametes for sexual reproduction

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9
Q

describe the process of sexual reproduction

A
  • Genes from two parents
  • Inherit mixture of features from both parents, so variation occurs
  • Females produce sex cells (gametes) called eggs and male gametes are called sperm
  • Gametes are formed by meiosis
  • A sperm and egg fuse together to make the offspring = fertilisation
  • When gametes fuse a zygote forms
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10
Q

Process of asexual reproduction

A
  • Genes from only one parent
  • All are clones (genetically identical) to the parent
  • Only mitosis is involved in asexual reproduction
  • No gametes (sex cells) involved
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11
Q

Advantages of asexual reproduction

A
  • Only one parent needed
  • Many identical offspring can be reproduced when conditions are favourable
  • Faster than sexual reproduction
  • More time and energy efficient as do not need to find a mate
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12
Q

Disadvantages of asexual reproduction

A
  • No variation
  • Susceptible to environmental change
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13
Q

Advantages of sexual reproduction

A
  • Produces variation in the offspring
  • If the environment changes variation gives a survival advantage by natural selection
  • Natural selection can be sped up by humans in selective breeding to increase food production
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14
Q

Disadvantages of sexual reproduction

A
  • Two parents are required, makes reproduction difficult for endangered species
  • More time and energy is required so fewer offspring are produced
  • Slower than asexual reproduction
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15
Q

What is fertilisation?

A
  • When gametes fuse to form a zygote
  • Gametes join at fertilisation to restore the normal number of chromosomes
  • The zygote then starts dividing through mitosis
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16
Q

What happens after fertilisation?

A
  • The zygote then starts dividing through mitosis
  • The number of cells increases
  • As the embryo develops cells differentiate
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17
Q

compare the processes of mitosis and meiosis

A

Mitosis
- cell divides once
- 2 cells are produced
- 46 chromosomes, the same number as the original cell
- used to make new body cells
- occurs in all parts of the body

Meiosis
- cell divides twice
- 4 cells are produced
- 23 chromosomes, half the number of chromosomes as the original cell
- how gametes are made
- happens only in testes and ovaries

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18
Q

what are the gametes in plants and animals?

A

flowering plants: pollen and egg cells
animals: sperm and egg cells

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19
Q

what are gametes?

A

Sex cells produced in meiosis

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20
Q

Explain why mutations in sex cells may be more serious than mutations in body cells

A

Mutations in sex cells will also affect the offspring, while mutations in body cells will only affect one individual

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21
Q

By which cell division type does asexual reproduction rely on?

A

Mitosis

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22
Q

How are gametes formed?

A

Meiosis

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23
Q

How is a gamete different from a normal body cell?

A

A gamete only contains half of the genetic information

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24
Q

Name the structure formed by fertilisation

A

Zygote

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25
Q

How many divisions do a cell undergo in meiosis?

A

2

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26
Q

describe the structure of fungi

A
  • Made up of a mass of thin threads called hyphae
  • The mass of the hyphae form the structure of fungi
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27
Q

Reproduction in fungi

A
  • Asexual most common
  • Toadstools etc are asexual fruiting bodies full of spores
  • In asexual reproduction the fungal spores are produced by mitosis and they are genetically identical to the parent
  • Some fungi also reproduce sexually in unfavourable conditions.
  • Two hyphae form different fungi join and the nuclei fuse
  • The new hypha has 2 sets of chromosomes
  • It then undergoes meiosis to make haploid spores, which are different from the original hyphae
  • Some of the spores may produce fungi better adapted to survive the adverse conditions
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28
Q

Are fungi haploid or diploid most of the time?

A

Haploid

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29
Q

When do two hyphae join together?

A

When the environmental conditions are unfavourable

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30
Q

Is mushroom asexual or sexual?

A

Asexual

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31
Q

When do fungi undertake meiosis?

A

After two hyphae have joined together

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32
Q

Which type of pathogen is malaria?

A

Protist

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33
Q

Which two types of cells are targeted by malaria in humans?

A

Liver cells and red blood cells

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34
Q

Malaria lifecycle - Where does fertilisation take place?

A

In the stomach of the mosquito

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35
Q

Malaria lifecycle - Where does asexual reproduction take place?

A

In the human host

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36
Q

What are the effects of malaria on humans?

A

Fever, loss of blood, brain damage, coma, death

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37
Q

Reproduction in malaria parasites

A
  • The malaria parasites has both sexual and asexual reproduction as part of its normal life cycle
  • The parasites in the human host are haploid and reproduce asexually by mitosis
  • When a female mosquito drinks blood containing these, the temperature drop makes them produce the sexual form, which burst out of the blood cells and fuse to form a diploid zygote
  • This undergoes meiosis, which introduces variation. Instead of forming gametes they form the asexual version of the parasite, which eventually get passed on to another human host
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38
Q

Reproduction in plants

A
  • Flowers are the sexual reproductive organs of plants
  • They make haploid gametes (pollen and egg cells) by meiosis that fuse to form diploid seeds that are genetically different to their parents
  • Many plants can also reproduce asexually, for example, strawberry plant runners or daffodil bulbs dividing
  • This involves only mitosis so the offspring are genetically identical to the parent
  • This is an advantage when flowers are destroyed or unfertilised or need to colonise areas quickly when conditions are good
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39
Q

What does the term haploid mean?

A

Each nucleus contains one set of chromosomes

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40
Q

What does the term diploid mean?

A

Each nucleus contains two sets of chromosomes

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41
Q

How many sets of chromosomes are there in each nucleus of normal fungal hyphae?

A

One

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42
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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43
Q

What is DNA?

A

The genetic material of the cell found in its nucleus

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44
Q

Structure of DNA

A

Spiral shape called a double helix

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45
Q

DNA nucleotides

A
  • The backbone of the long stand of DNA is made of alternating sugar and phosphate molecules. Attached to each sugar is one of four bases
  • The combination of a sugar, phosphate and a base is a nucleotide
  • The DNA polymer is made of repeating nucleotide units
46
Q

What is a gene?

A
  • A small section of DNA on a chromosome
  • Each gene codes for a particular sequence of amino acids, to make a specific protein
47
Q

What are the four bases of DNA?

A

A, T, C, G

48
Q

DNA Base pairs

A

A and T
C and G

  • Base pairs hold the two strands of the DNA helix together
  • It is the sequence of these bases along a DNA molecule that forms the genetic code
49
Q

Which two molecules make up the backbone of the DNA?

A

Sugar and phosphate

50
Q

What is a nucleotide?

A

The combination of phosphate, sugar and a base which, when in a repeating unit makes the DNA polymer

51
Q

What is a genome?

A
  • All the genetic material of an organism
  • It includes all of the chromosomes, and the genetic material found in the mitochondria as well
  • The human genome has the ability to make many different proteins from the same gene by suing it in different ways, or switching part of a gene on or off
52
Q

Which is larger, a gene or a chromosome?

A

Chromosome

53
Q

Where in the cell is DNA used to produce mRNA?

A

Nucleus

54
Q

Allele

A

A gene or a combination of genes that we receive from our parents

55
Q

Genotype

A

Combination of alleles

56
Q

Phenotype

A

An organism’s observable characteristics due to interactions of the genotype

57
Q

Dominant allele

A

Expressed in the phenotype

58
Q

Recessive allele

A

Not expressed in the phenotype, unless the combination includes double recessive alleles

59
Q

Homozygote

A

An individual with two identical alleles for a characteristic
For example, BB, bb

60
Q

Heterozygote

A

An individual with different alleles for a characteristic
For example, Bb

61
Q

Definition of genome

A

All the genetic material of an organism

62
Q

Definition of chromosome

A

A large molecule of DNA containing many genes

63
Q

Definition of gene

A

A small section of DNA on a chromosome

64
Q

Definition of DNA

A

A polymer with a double helix structure, formed of many nucleotides

65
Q

Definition of nucleotide

A

A molecule made up of a sugar, a phosphate group, and one of four different bases

66
Q

Definition of ribosome

A

Where protein synthesis takes place

67
Q

Definition of base

A

Nitrogenous compounds that make up part of the structure of DNA and RNA. They are represented by the letters A, T, C, and G

68
Q

Definition of protein

A

Large molecules made up of many amino acids bonded together

69
Q

Where in the cells are proteins made?

A

Ribosomes

70
Q

Explain the process of protein synthesis

A
  • Genes in the DNA produce a template for the protein
  • The template reflects the sequence of bases but it is small enough to fit through the nuclear pore
  • The template binds to the ribosome surface
  • Carrier molecules, each attached to a specific amino acid attach themselves to the template in the order given by the DNA
  • The amino acids are joined together to form a specific protein
  • Carrier molecules keep bringing specific amino acids to add to the growing protein chain in the correct order until the template is completed
  • The protein detaches from the carrier molecules and the carrier molecules detach from the template and return to the cytoplasm to pick up more amino acids
  • The protein chain then folds up in to the unique shape of the protein
71
Q

How many base codes for an amino acid?

A

3

72
Q

What brings amino acids to the ribosomes?

A

Carrier molecule (tRNA)

73
Q

Name three uses of proteins in the body

A
  • Enzymes
  • Antibodies
  • Hormones
74
Q

Why can’t DNA move into the cytoplasm?

A

It is too large to move through the nuclear pores

75
Q

What is transcription?

A

The process of making mRNA from DNA

76
Q

What is the function of the non-coding regions of DNA?

A
  • Non-coding regions are the parts of DNA in between the genes
  • Non-coding parts switch genes on or off, so variations in these areas of DNA can affect how genes are expressed
  • When the gene is switched on they make the protein, when it is turned off the gene stops making the protein
77
Q

Effects of a mutation

A
  • No change in amino acids or a slight change which doesn’t effect the protein structure
  • Altered protein, so the protein may not work e.g. active site of enzyme may no longer fit substrate
  • Mutation within non-coding region nearby to a gene may effect the expression (production) of a protein
78
Q

Mutations - mitosis vs meiosis

A

Mitosis
- affects localised cells

Meiosis
- affects the whole organism

79
Q

Explain how a change in one amino acid in an enzyme molecule could stop the enzyme working

A

If there is a mutation in an amino acid in an enzyme molecule, the enzyme’s structure could be altered and a different protein would be formed. The active site of the enzyme may be changed and no longer fit the substrate.

80
Q

Explain how DNA controls the synthesis of proteins in a cell

A
  • Template (mRNA) is produced that reflects sequence of bases in DNA of a single gene
  • Template is small enough to leave the nucleus through the nuclear pores, and binds to the surface of the ribosome in the cytoplasm
  • Carrier molecules (tRNA) in the cytoplasm, each attached to a specific amino acid, attach themselves to template in order given by DNA until template completed
  • Amino acids join together to form specific protein
  • Protein detaches from carrier molecules, which detach from template and return to cytoplasm to pick up more amino acids
  • Once protein chain is complete, the molecule folds up to form a unique shape that will enable it to carry out its function in the cell
81
Q

What is the difference between genotype and phenotype?

A

Genotype is the genetic makeup/alleles present whereas phenotype is the resulting characteristic

82
Q

Name the three parts of a DNA molecule

A

Sugar, phosphate, base

83
Q

Where in the cell are proteins synthesised?

A

Ribosomes

84
Q

Is cystic fibrosis caused by a dominant or recessive allele?

A

Recessive

85
Q

What is a change in a DNA sequence called?

A

Mutation

86
Q

What is cystic fibrosis caused by?

A

Caused by a single recessive allele, which means that only homozygous individuals will develop the disease

87
Q

What is cystic fibrosis a disorder of?

A
  • Affects the respiratory and digestive systems by producing abnormally thick mucus
  • Affects the cell membranes in the lungs and intestines
88
Q

What are the symptoms of cystic fibrosis?

A

Symptoms often develop during early childhood
Thick mucus clogs the airways leading to:
- breathlessness and coughs
- repeated chest infections, bacteria trapped and thrive in the thick mucus
Mucus can block pancreatic duct and block enzyme secretion which can lead to low weight gain

89
Q

What is polydactyly caused by?

A

Caused by a dominant allele, so can be passed on by just one parent

90
Q

What are the symptoms of polydactyly?

A

Abnormal number of fingers and toes

91
Q

Why would a blocked pancreatic duct lead to low weight gain in sufferers of cystic fibrosis?

A

Mucus blocks enzyme secretion so food cannot be digested. If the food is not digested the body cannot store it as anything including weight.

92
Q

What is polydactyly a disorder of?

A

Disorder in the regulation of genetic sequencing (that forms limbs)

93
Q

Embryo screening

A

All methods take cells from the embryos so that their DNA can be analysed for genetic disorders

94
Q

What are the three methods of embryo screening?

A
  • Chorionic villus sampling
  • Amniocentesis
  • Pre-implantation genetic screening (in IVF only)
95
Q

Chorionic villus sampling

A
  • Sample of placental tissue taken through wall of abdomen or vagina
  • 10-12 weeks
  • 1-2% miscarriage risk
96
Q

Amniocentesis

A
  • Needle inserted into amniotic fluid to collect cells from placenta and foetus
  • 15-16 weeks
  • 0.5-1% miscarriage risk
97
Q

Pre-implantation genetic screening

A
  • For use in IVF before the embryo is implanted
  • Embryos are analysed for genetic disorders or defects
98
Q

IVF Process

A
  • Egg donor is given fertility drugs
  • Multiple eggs are produced and collected from the ovaries
  • Eggs are fertilised to produce embryos
  • Embryos analysed for genetic defects
  • Only healthy embryos are injected into uterus
  • Mother gives birth to genetically healthy baby
99
Q

Where are cells taken from in chorionic villus sampling?

A

Placenta

100
Q

Which method has the highest chance of miscarriage?

A

Chorionic villus sampling

101
Q

Which method is only possible using IVF?

A

Pre-implantation genetic screening

102
Q

What is the purpose of screening for genetic disorders?

A

To identify the possibility of the child having a genetic disorder, so the parents can decide whether to terminate the pregnancy or in order to prepare for having a child with a genetic disorder

103
Q

Advantages of embryonic screening

A
  • Can prepare and reduce high societal cost of health care and support for raising a child with a genetic disorder
  • Could avoid children being born into pain or suffering caused by genetic disorders
104
Q

Disadvantages of embryonic screening

A
  • Religious issues: everything should have the potential of life
  • Collecting cells from foetus increases the risk of miscarriage
  • Screening necessitates decisions about termination
  • Could give rise to ‘designer babies’ a baby whose genetic makeup has been selected or altered
  • Screening is expensive
  • No current cures for genetic disorders identified in screening
  • Screening is not entirely reliable, can give false positive or negative results
105
Q

Describe what happens when a cell divides to form gametes

A
  • Copies of the genetic information are made
  • The cell divides twice to form four gametes, each with a single set of chromosomes
  • All gametes are genetically different from each other
106
Q

Describe examples of organisms that reproduce both by asexual and sexual reproduction

A
  • Malarial parasites reproduce asexually in the human host, but sexually in the mosquito
  • Many fungi reproduce asexually by spores but also reproduce sexually to give variation
  • Many plants produce seeds sexually, but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils
107
Q

Why is meiosis important for sexual reproduction?

A
  • It increases genetic variation
  • It ensures that the zygote formed at fertilisation is diploid
108
Q

What are DNA nucleotides made of?

A
  • A sugar
  • A phosphate
  • One of the four bases: A, T, C, G
109
Q

Explain how a gene codes for a protein

A
  • A sequence of three bases in a gene forms a triplet
  • Each triplet codes for an amino acid
  • The order of amino acids determines the structure and function of protein formed
110
Q

What are the two stages of protein synthesis?

A

Transcription and translation

Biology Paper 2 (10 decks)

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