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Z: GCSE Biology > B1 - You and Your Genes > Flashcards

B1 - You and Your Genes Flashcards

1
Q

Differences between individuals of the same species are called a) which can be due to b) or c).

A

a) Variation
b) Genetic factors (e.g. dimples, eye colour)
c) Environmental factors (e.g. scars, hairstyle.)

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2
Q

a) What is the function of genes?

b) Different genes control different what?

A

a) Carrying the information needed for you to develop

b) Characteristics

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3
Q

a) Where
and
b) How
are genes found?

A

a) Inside the nucleus of every cell

b) In long strings called chromosomes

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4
Q

Chromosomes are made of DNA molecules. DNA molecules are made up of a) and are coiled to form a b).

A

a) two very long strands

b) double helix

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5
Q

DNA molecules form a complete set of instructions for what 2 things?

A
  • How the organism should be constructed

- How each cell should function

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6
Q

Genes are sections of DNA. Genes control the development of different characteristics by giving instructions to the cell.

a) The cell carries out these instructions by producing what?
b) What are the two types of a) and what are their functions? Give one example of a) for each type.

A

a) Proteins
b) - Structural proteins (for cell growth or repair, e.g. collagen)
- Functional proteins (enzymes to speed up chemical reactions, e.g. amylase)

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7
Q

Different species have different numbers of chromosome pairs. How many pairs do human cells contain?

A

23 pairs. (46 in total)

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8
Q

Chromosomes normally come in pairs.

a) What type of cell defies this rule, as it only contains singular chromosomes?
b) Why is this?

A

a) Sex cells.
b) The sperm contains 23 chromosomes, as does the egg, so when fertilised there are 46 chromosomes in 23 pairs (half from the egg of the mother and half from the sperm of the father)

Sperm (23) + Egg (23) = Fertilised egg cell (46/23 pairs)

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9
Q

a) What is an allele?

b) Give an example of an allele.

A

a) Different versions of the same gene.

b) The gene for dimples has 2 alleles - to have dimple and to not have dimples.

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10
Q

If a gene contains 2 alleles, where does each one come from within a gene?

A

One allele would be inherited from the father, and the other from the mother.

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11
Q

What is the definition of homozygous?

A

Inheriting 2 alleles that are the same.

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12
Q

What is the definition of heterozygous?

A

Inheriting 2 alleles that are different.

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13
Q

True or false?

Brothers and sisters randomly inherit different combinations of alleles, which is why they can be very different.

A

True.

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14
Q

The combination of alleles you have is called your a) and the actual characteristics you show is called your b). (HT)

A

a) Genotype

b) Phenotype

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15
Q

What is meant by the term ‘dominant allele’?

A

Controls the development of a characteristic, even if it’s only present on one chromosome in a pair.

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16
Q

What is meant by the term ‘recessive allele’?

A

Controls the development of a characteristic only if a dominant allele is not present, i.e. if the recessive allele is present on both chromosomes in a pair.

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17
Q

How is a dominant allele shown as on a genetic diagram?

A

Capital letter

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18
Q

How is a recessive allele shown as on a genetic diagram?

A

Lower-case letter

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19
Q

What is the purpose of a genetic diagram?

A

They are used to show all the possible combinations of alleles and outcomes for a particular gene.

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20
Q

Give 2 examples of a genetic diagram.

A
  • Punnet squares

- Family trees

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21
Q

True or False?

In both male and female sex genes, the chromosomes are identical.

A

False.

  • In females, the pair of sex chromosomes are identical and are both X chromosomes.
  • In males, one chromosome will be an X chromosome and the other will be a Y chromosome.
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22
Q

a) Explain what happens during fertilisation of egg and sperm that defines the gender of the offspring being produced.
b) Why is this? (HT)

A

a) If an “X” sperm fertilises an egg (“XX”), a girl is produced. If a “Y” sperm fertilises an egg (“XX”), a boy is produced.
b) - Sex of an individual is determined by the sex-determining region Y (SRY) gene on the Y chromosome
- If the gene isn’t present/two X chromosomes, the embryo will develop into a female
- If it is present/XY chromosomes, testes develop the hormone androgen, detected by receptors in the embryo which allow male reproductive organs to grow.
- If it’s XY but the androgen is not detected, female sex organs (apart from the uterus) develop, but the female will be infertile.

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23
Q

What are the symptoms of Huntington’s disease?

A

Involuntary movement, clumsiness, memory loss, mood changes and an inability to concentrate.

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24
Q

When do symptoms of Huntington’s disease usually occur?

A

During adulthood, which means the sufferers may have already passed it on to their children.

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25
Q

True or False?

Cystic fibrosis is a disease that affects cell membranes, causing a thick, sticky mucus in the lungs, gut and the pancreas.

A

True.

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26
Q

What are 4 of the symptoms of cystic fibrosis?

A
  • Weight loss
  • Difficulty in breathing
  • Chest infections
  • Difficulty digesting food
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27
Q

Unlike Huntington’s disease, the cystic fibrosis allele is __________?

A

Recessive.

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28
Q

The cystic fibrosis allele is recessive, which means what?

A

If a person only possesses one allele for cystic fibrosis, they will have no symptoms of the disorder at all. However, they are called carriers because they could possibly pass on the allele to their children.

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29
Q

What is meant by a carrier of a genetic disease?

A

Someone who could possibly pass on the disease to a child, but doesn’t have it themselves.

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30
Q

True or False?

It’s not possible to test someone for a faulty allele.

A

False - It’s possible to test a person for a faulty allele.

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31
Q

Tests can be done to see if an adult possesses a disease-causing allele in their cells. If a positive result is obtained, what might this mean?

A

The adult may choose not to have any children and perhaps choose to adopt a child instead.

Alternatively, the adult may still decide to have a child and accept the risk of passing on the disorder to their offspring.

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32
Q

Why might children be tested to see if they have any disease-causing genes?

A

So that possible preventative measures can be taken. Tests might also be carried out before prescribing certain drugs (e.g. for cancer treatment) that might have a bad affect on an individual.

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33
Q

What risk would testing the fluid surrounding the fetus or the placenta for faulty alleles have?

A

Possibility of having a miscarriage or other things.

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34
Q

a) What might happen if a faulty allele was detected through the testing of amniotic fluid?
b) What are the ethical issues within this?

A

a) Parents might have to decide if the pregnancy should be terminated and whether other family members should be told as they may too carry the faulty allele.
b) Many ethical issues surround whether or not having an abortion is right or not.

35
Q

What is the name of the fluid that surrounds the fetus and/or placenta?

A

Amniotic fluid.

36
Q

No test is 100% reliable. For each of the possible outcomes listed below, state what the test result would be, and the reality.

a) True positive outcome
b) True negative outcome
c) False positive outcome
d) False negative outcome

A

a) Test result = Fetus has the disorder
Reality = Fetus has the disorder

b) Test result = Fetus doesn’t have the disorder
Reality = Fetus doesn’t have the disorder

c) Test result = Fetus has the disorder
Reality = Fetus doesn’t have the disorder

d) Test result = Fetus doesn’t have the disorder
Reality = Fetus has the disorder

37
Q

What questions should be addressed before genetic testing can become common practice? (3 things)

A
  • How can mistakes be prevented?
  • Is it right to interfere with nature?
  • Who has the right to decide is a disorder is worth living with?
38
Q

What might genetic testing be used to screen individuals for?

A
  • Susceptibility to certain diseases or conditions

- Possible problems with certain prescribed drugs or treatments

39
Q

It has been suggested that babies should be screened at birth, allowing doctors to do what?

A
  • To tailor healthcare and prevent problems

- To stop genetic disorders from being passed on, eliminating them completely.

40
Q

Give one point for each point of view about genetic testing. (for and against)

A
  • One view is that this would mean less suffering and the money currently spent on treatment for genetic diseases could be used elsewhere
  • The opposing view is that these disorders are natural and it would be wrong to eliminate them
41
Q

True or False?

Storing genetic information could raise questions about confidentiality.

A

True.

If employers or insurance companies had access to an individual’s genetic information, it might be used to discriminate and people might be turned down for jobs or life insurance if they are found to have a higher risk of illness.

42
Q

Explain what embryo selection is. (HT)

A

Embryo selection is another way of preventing babies from having genetic disorders.

43
Q

Why is embryo selection a controversial topic? (HT)

A
  • Some people believe it’s unnatural

- There are concerns that people could select certain characteristics of their choosing (such as eye colour or gender).

44
Q

Pre-selection of a baby’s characteristics (such as gender or eye colour) could reduce what? (HT)

A

Variation, for example if most people selected blue eyes for their baby, the brown eye allele could disappear over time.

45
Q

The procedure for embryo selection is called what? (HT)

A

Pre-implantation Genetic Diagnosis (PGD)

46
Q

What happens within the PGD procedure? (HT)

A
  • After fertilisation the embryos are allowed to divide into eight cells before a single cell is removed from each one for testing.
  • The cells are then tested to see if they carry the alleles for a specific genetic disorder.
47
Q

Embryos for embryo selection can be produced through IVF. What happens in this process? (HT)

A
  • Ova are harvested from the mother and fertilised.
  • The embryos are tested for the faulty allele.
  • Healthy embryos are implanted into the uterus. The pregnancy then proceeds as normal.
48
Q

What does IVF stand for? (HT)

A

In-vitro fertilisation

49
Q

What does PGD stand for? (HT)

A

Pre-implantatic Genetic Diagnosis

50
Q

a) Bacteria and other single-cell organisms can reproduce by doing what?
b) What is this process called?

A

a) Dividing to form two ‘new’ individuals.

b) Asexual reproduction

51
Q

True or False?

When bacteria and other single-cell organisms divide to form two new individuals, these new individuals are clones (genetically identical to the parent cell).

A

True.

52
Q

True or False?

It is rare that plants can reproduce asexually.

A

False - Most plants and some animals can reproduce asexually.

53
Q

Variation in organisms that reproduce asexually is normally only cause by what?

A

Environmental factors.

54
Q

How can animal clones occur naturally?

A
  • The cells of an embryo sometimes separate

- The two new embryos develop into identical twins

55
Q

How can animal clones be produced artificially?

A
  • The nucleus from an adult body cell is transferred into an empty (nucleus removed) unfertilised egg cell
  • The new individual will have exactly the same genetic information as the donor.
56
Q

Why are there conflicting views on artificial animal cloning? (HT)

A

Some see the process as unnatural and unethical. However, the technology is being closely monitored and regulated by the Government.

57
Q

Explain the four stages of cell division during asexual reproduction.

A
  • Parental cell with two pairs of chromosomes
  • Each chromosome replicated itself
  • The copies are pulled apart. Cell now divides for the only time.
  • Each ‘daughter’ cell has the same number of chromosomes and contains the same genes as the parental cell.
58
Q

Many plants produce clones when they form what?

A

Either bulbs or runners

59
Q

a) What are bulbs?

b) What is an example of a bulb?

A

a) Bulbs are swollen leaves that act as a store over the non-growing season. They develop into new plants in the following, and subsequent, seasons.
b) Daffodils.

60
Q

a) What are runners?

b) What is an example of a runner?

A

a) Runners are stem-like outgrowths along which new plants in the following, and subsequent, seasons.
b) Strawberry plants.

61
Q

What do bulbs and runners allow plants to do?

A

Survive and reproduce without the meeting of male and female sex cells. But, as the new plants are clones and no genetic variation is taking place, they will all be susceptible to the same diseases as the parent plant.

62
Q

What are ‘gametes’?

A

Sex cells.

63
Q

What is a stem cell?

A

An unspecialised cell

64
Q

True or False?

Most organisms are made up of various specialised cells with different structures.

A

True.

65
Q

True or False?

In early stages of development, cells are very much specialised.

A

False - In the early stages of development, cells are not specialised (these are stem cells).

66
Q

What do stem cells have the potential to do?

A

Develop into any type of cell, which could replace damaged tissues, e.g. in patients with Parkinson’s disease.

67
Q

What are the two types of stem cell?

A
  • Adult stem cells

- Embryonic stem cells

68
Q

Where are adult stem cells taken from?

A

Areas that are adapted for the replacement and repair of tissues, such as umbilical cord blood and bone marrow.

69
Q

True or False?

Adult stem cells have the potential to develop into a range of specialised cells, but not all types.

A

True.

70
Q

Where are embryonic stem cells taken from?

A

A developing embryo, so to produce them it’s necessary to clone embryos

71
Q

Embryonic stem cells have the potential to do what?

A

Develop into any kind of specialised cell.

72
Q

Why are some people against stem cell technology?

A

Because they might think it’s unnatural/unethical.

73
Q

Why will someone with only one allele for Huntington’s disease definitely develop the disease?

A

Because the allele for Huntington’s is dominant.

74
Q

Why are genetic tests carried out on fetuses?

A

To see if the fetus has any faulty alleles/genes

75
Q

A stem cell taken from bone marrow is what type of stem cell?

A

An adult stem cell.

76
Q

What part of the body does Huntington’s disease affect?

A

The central nervous system, and also damages the brain’s nerve cells.

77
Q

What is Huntington’s disease caused by?

A

A faulty gene on the 4th pair of chromosomes

78
Q

True or False?

Huntington’s disease is a perfectly curable disease.

A

False - Huntington’s is incurable and leads to premature death

79
Q

Huntington’s disease brings gradual changes to the body which develop into what?

A

The symptoms of the disease

80
Q

A gene provides instructions to make what? Is it:

a) Chromosomes
b) Proteins
c) Nuclei
d) Cells

A

b) Proteins

81
Q

Different versions of the same gene are called what? Is it:

a) DNA
b) pairs
c) gametes
d) alleles

A

d) alleles

82
Q

Niamh is growing yeast, a single-celled fungus, in an experiment. She adds a small sample of the yeast to a growth mixture. After a few days, there’s more yeast in the flask than she had to start with.

Complete the sentences below, using the words at the very bottom.

The cells that make up Niamh’s skin contain 23 pairs of _____a)_____. Yeast produce via ____b)_____ reproduction. All the yeast are genetically identical, therefore they’re _____c)_______. The yeast don’t look exactly the same. This is due to ____d)______ factors.

asexual; sexual; genetic; environmental; chromosomes; nucleus; clones

A

a) chromosomes
b) asexual
c) clones
d) environmental

83
Q

The sex of an individual is determined by a pair of chromosomes. Males have one X and one Y chromosome; females have a pair of X chromosomes.

Explain why the sperm are said to ‘decide’ the sex of the baby.

A

Half the sperm carry an X chromosome and half the sperm carry a Y chromosome. All the eggs (ova) carry an X chromosome, so which type of sperm fertilises the egg decides whether the baby is female (XX) or male (XY)

84
Q

What is the meaning of genotype? (HT)

A

Genetic makeup; types of alleles present (in the nucleus)

Z: GCSE Biology (11 decks)

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