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Biology B123 > B1 - You and your genes > Flashcards

B1 - You and your genes Flashcards

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1
Q

What are genes?

A

Instructions that control how an organism develops and functions.

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2
Q

Where are genes found?

A

In the nucleus of its cells.

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3
Q

How do genes work?

A

They tell the cells to make proteins needed for your body to work.

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4
Q

What is DNA?

A

A very long molecule that determines the order of amino acids in a protein (according to the order of the 4 bases)

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5
Q

What does DNA consist of?

A

Chromosomes, bases, phosphates and sugar molecules.

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6
Q

What is a Chromosome?

A

Thread-like structures in the nucleus of the cell that carry genetic information.

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7
Q

What are the two types of proteins?

A
  1. FUNCTIONAL: Enable the body to function.
    Examples: ENZYMES, ANTIBODIES and HORMONES.
  2. STRUCTURAL: Give the body structure, rigidity and strength.
    Examples: Collagen in ligaments, keratin in skin.
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8
Q

What is a genome?

A

A complete gene set of an organism.

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9
Q

What are our characteristics controlled by?

A

Genes (e.g. dimples), our Environment (e.g. scars), or a COMBINATION of these (e.g. weight)

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10
Q

What do differences in genes produce in terms of offspring?

A

A VARIATION in offspring.

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11
Q

What are some characteristics controlled by? What do these show?

A

Some are controlled by several genes working together. These show CONTINUOUS VARIATION across a population, e.g. the continuous range of eye colour.

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12
Q

What do our body cells contain? What do our sex cells contain?

A

Our body cells contain 23 PAIRS OF CHROMOSOMES
( = 46)
Sex cells contain only ONE CHROMOSOME from each pair ( = 23)

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13
Q

What are alleles? How many alleles does an individual usually have for each gene?

A

The different forms in which the genes controlling a characteristic can occur. An individual usually has two alleles for each gene.

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14
Q

What is an example of alleles?

A

Dimples: there is one allele for the presence of dimples and another allele for the lack of dimples.

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15
Q

What does HOMOZYGOUS mean?

A

When the two alleles of a gene are identical. (e.g. DD)

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16
Q

What does HETEROZYGOUS mean?

A

When the two alleles of a gene are different. (e.g. Dd)

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17
Q

What happens at fertilisation?

A

An egg and sperm join together to produce a zygote.

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18
Q

What is a zygote?

A

A full set of 46 chromosomes - 23 from father, 23 from mother.

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19
Q

Why do offspring have some similarities to their parents?

A

Because of the combination of maternal and paternal alleles in the fertilised egg.

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20
Q

Why is that different offspring from the same parents can differ from each other?

A

Because they inherit a different combination of maternal and paternal alleles.

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21
Q

Alleles for a trait can either be ______ or ______

A

DOMINANT or RECESSIVE.

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22
Q

How are dominant alleles written in genetic diagrams?

A

With UPPER-CASE letters, e.g. H for hairy toes.

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23
Q

How are recessive alleles written in genetic diagrams?

A

With LOWER-CASE letters, e.g. h for hairless toes.

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24
Q

An individual with ONE OR BOTH dominant alleles will….?

A

SHOW the associated DOMINANT characteristic

e.g. HH or Hh will show hairy toes

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25
Q

An individual with ONE recessive allele will….?

A

NOT SHOW the associated recessive characteristic

e.g. Hh will still show hairy toes NOT hairless toes

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26
Q

An individual with BOTH recessive alleles will…?

A

SHOW the associated RECESSIVE characteristic

e.g. hh will show hairless toes

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27
Q

What are the two ways in which we can visualise the genetic inheritance of a trait?

A
  1. Punnett Square
    (can show genetic crosses and the probability of two parents producing different types of offspring)
  2. Family Tree Diagram
    (shows the inheritance of a trait/genetic disorder)
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28
Q

What does the 23rd pair of chromosomes determine?

A

Our SEX (Male/Female)

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29
Q

Males have __ sex chromosomes.

Females have __ sex chromosomes.

A

Males have XY sex chromosomes.

Females have XX sex chromosomes.

30
Q

What does the sex-determining gene on the Y chromosome trigger?
What does the sex-determining gene on the X chromosome trigger?

A

Y - The development of testes.

X - The development of ovaries.

31
Q

If a defective gene is found on a part of an X chromosome, what can this result in?

A

A sexlinked disorder.

32
Q

What are 2 examples of sex-linked diseases?

Are this likely to be present in males or females?

A
  1. Haemophilia (blood clotting disorder)
  2. Red-green colorblindness

They are far more likely to be present in males.

33
Q

What is a genotype?

A

A person’s genetic makeup. (e.g. DD for dimples.)

34
Q

What is a phenotype?

A

A person’s observable physical features.

35
Q

Why do identical twins have identical genotypes?

A

They develop after a fertilised egg splits into two.

36
Q

What are a small number of disorders caused by?

A

Defective/Faulty alleles of a single gene.

37
Q

What are the 2 main examples of genetic disorders caused by faulty alleles?

A
  1. Huntington’s disease

2. Cystic fibrosis

38
Q

What is Huntington’s disease caused by?

A
  • Caused by DOMINANT alleles. The presence of a SINGLE dominant allele will cause the disease, e.g. Hh or HH makes you a SUFFERER.
39
Q

When does Huntington’s disease occur?

What are 5 symptoms of Huntington’s disease?

A

It occurs in middle age (late-onset)

Symptoms include: tremor, clumsiness, memory loss, inability to concentrate, mood changes.

40
Q

What is cystic fibrosis caused by?

A

-Caused by RECESSIVE alleles. The presence of BOTH recessive alleles will cause the disease, e.g. hh will make you a SUFFERER.

41
Q

What are 4 symptoms of cystic fibrosis?

A
  1. Thick mucus
  2. Difficulty breathing
  3. Chest infections
  4. Difficulty in digesting food.
42
Q

You can become a CARRIER of a recessive disorder, such as cystic fibrosis, if…?

A

You have AT LEAST one single recessive allele in a pair. (e.g. Ff makes you a carrier, not a sufferer.)

43
Q

What is genetic screening?

A

A screening used to check for a particular disorder, even when there is no history of it in the family.

44
Q

What is genetic testing?

A

A test used to check if there is a genetic disease (e.g. cystic fibrosis) that runs in the family.

45
Q

Why is genetic testing beneficial (1) ?

A

It allows people to get treatment for the disease or to plan for the future.

46
Q

What are 5 things to consider, in terms of ethical concerns, about genetic testing?

A
  1. The results are not 100% accurate (false positive, false negative)
  2. There’s a chance of miscarriage during tests.. (0.5 - 1%)
  3. Is it right to terminate a pregnancy?
  4. Discrimination from employers
  5. Insurance companies may refuse to give life insurance
47
Q

What are two types of CELL SAMPLING of genetic testing during pregnancy?

A
  1. Amniocentesis (collecting cells from the developing fetus which are present in amniotic fluid)
  2. Chorionic villus sampling (testing a sample of cells taken from placenta)
48
Q

Why is embryo screening used?

A

To investigate families with a known history of a disorder, such as cystic fibrosis. It allows doctors to remove any embryos suffering from a disorder and implant only embryos.

49
Q

What is the scientific name for screening embryos prior to implantation and only using healthy embryos?

A

Pre-implantation genetic diagnosis (PGD)

50
Q

What do guidelines in clinics and research centres cover in terms of these screenings?

A

They cover ethical and moral considerations for embryo use.

51
Q

What are the 2 decisions that parent are likely to make when passing on a genetic abnormality?

A
  1. May decide to not have a family

2. May need to decide on whether to continue with the pregnancy or terminate it.

52
Q

What is false negative?

What is false positive?

A

False negative - when a patient is told that they are healthy but the actual results show that they are actually sufferers/carriers of a disease.

False positive - when a patient is told that they are sufferers/carriers of a disease but the actual results show that they are healthy.

53
Q

What are clones?

A

Individuals with identical genes

54
Q

What DNA is present in the offspring in asexual reproduction?

A

The offspring has IDENTICAL DNA to the parent.

55
Q

What are 3 examples of organisms that reproduce asexually?

A
  1. Bacteria
  2. (Some) plants
  3. Simple animals, e.g. Hydra
56
Q

What are the 2 ways in which plants can reproduce asexually?

A
  1. Using runners (e.g. strawberries) - shoots sent out that grow into identical plants.
  2. Producing bulbs (e.g. daffodils)
57
Q

How are human clones (i.e. identical twins) produced?

A

When a fertilised egg splits, resulting in two genetically identical individuals.

58
Q

As clones have identical DNA, any differences between individuals in a clone and their parent MUST be a result of…..?

A

The ENVIRONMENT and NOT genes.

59
Q

What are 2 advantages of producing clones/asexual reproduction?

A
  1. Successful characteristics are seen in offspring

2. Asexual reproduction is useful where plants and animals live in isolation.

60
Q

What is the main disadvantage of producing clones/asexual reproduction?

A

There is no genetic variation.

This means that if conditions change or there is disease, the population could be wiped out.

61
Q

What are 2 examples of artificial animal cloning?

A
  1. Dolly the Sheep

2. Snuppy the Dog

62
Q

How does artificial animal cloning work?

Describe the 3 stages.

A
  1. Nucleus from a body cell is extracted.
  2. Nucleus is inserted into an egg cell that has had its nucleus removed. This gives the egg cell a full set of genes without having fertilised.
  3. The embryo is implanted into a suitable surrogate mother.
63
Q

Why do people not create clones of humans

(in many countries, including the UK) ?

A

It is ILLEGAL to create clones of humans in many countries.

64
Q

What is differentiation?

A

When most of the cells (which soon develop into a baby) become specialised to do different jobs.

65
Q

After five days of fertilisation, how does the embryo develop?

A

The embryos become a ball of cells containing EMBRYONIC STEM CELLS.

66
Q

What type of stem cells remain in certain parts of our bodies?

A

ADULT stem cells.

67
Q

What can adult stem cells perform?

A

They can repair/replace certain cell types.

For example, bone marrow cells are able to develop into different types of blood cells.

68
Q

What is the benefit of using adult stem cells?

What is the main drawback of adult stem cells?

A

Benefit - They can be used to treat various diseases.

Drawback - They have limited uses.

69
Q

What makes embryonic stem cells have such huge potential?

A

They can develop into ANY cell types.

70
Q

What are 2 reasons as to why using embryonic stem cells are controversial?

A
  1. They are usually taken from unused embryos following fertility treatments.
  2. Their use involves the destruction of the embryo.
71
Q

What is recent research focusing on, in terms of the use of embryonic stem cells?

A

They are focusing on reprogramming adult body cells into stem cells, and collecting cells from the umbilical cord blood when a baby is born.

72
Q

What are 3 uses of stem cells?

A
  1. The testing of new drugs
  2. Understanding how cells become specialised in the early stages of human development by the switching on/off of particular genes.
  3. Renewing damaged/destroyed cells in spinal injuries, heart disease, Alzheimer’s disease and Parkinson’s disease.

Biology B123 (3 decks)

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