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Biology GCSE > Inheritance And Genes > Flashcards

Inheritance And Genes Flashcards

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1
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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2
Q

DNA has a _________ structure

A

-double helix
- because it has two strands

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3
Q

What is a chromosome

A
  • A long molecule of DNA found in the nucleus
  • Each chromosome carries many genes
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4
Q

How many chromosomes are there in a typical human cell?

A

Humans have 23 pairs of chromosomes, so 23 x 2 = 46 chromosomes in total.

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5
Q

Chromosomes exist in pairs. The chromosomes in the 23rd pair are known as the

A

Sex chromosomes

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6
Q

Do women have XX or XY sex chromosomes?

A

XX

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7
Q

What is a Gene

A

A small section of DNA that codes for a specific protein

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8
Q

How does DNA code for proteins

A

DNA can code for proteins by coding for the sequence in which amino acids are joined together.

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9
Q

What does the term ‘genome’ mean?

A

The entire set of genetic material in an organism

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10
Q

What are inherited diseases

A
  • genes that cause diseases can be inherited by offspring
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11
Q

What can understanding genomes of other people mean

A

It can tell us about the migration patterns of our ancestors.

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12
Q

Where are the chromosomes found in the cell?

A

Nucleus

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13
Q

Alleles are…

A

Alleles are the different versions of a particular gene.

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14
Q

Our body cells contains ___ copies of….

A

-Our body cells contain two copies of each chromosome
- one from our mother, and one from our father.
- This means that we also have two versions of each gene (each different version is a different allele).

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15
Q

Homozygous

A

If both alleles are the same

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16
Q

Alleles can be either

A
  • dominant
  • recessive
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17
Q

Charlie is heterozygous with one dominant allele and one recessive allele.

Which allele will be expressed?

A
  • dominant one
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18
Q

In order to be expressed, how many recessive alleles must be present?

A

2

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19
Q

What is the genotype

A
  • an individual’s collection of genes
  • the two alleles present for a particular gene
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20
Q

What is a phenotype?

A

The characteristics an organism expresses’ as a result of their genotype

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21
Q

If a mouse has one allele for brown fur, and another allele for black fur, would they be considered homozygous or heterozygous for that gene?

A

Heterozygous

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22
Q

Do animals usually reproduce via sexual or asexual reproduction?

A

Sexual

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23
Q

Which process is used to create gametes?

A

Meiosis

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24
Q

What do we call the fusion of male of female gametes?

A

Fertilisation

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25
Q

Sexual reproduction involves…

A
  • the combination of DNA from two different parents.
  • This means that the offspring will be genetically different to either of their parents.
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26
Q

Sperm and egg cells are haploid cells and only have __ chromosomes

A

23

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27
Q

When a sperm fertilises the egg though, they form ____ which has ___ chromosomes

A

When a sperm fertilises the egg though, they form a diploid cell that has 46 chromosomes.

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28
Q

During sexual reproduction in plants, which two gametes fuse together?

A

Pollen and egg

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29
Q

How many parents are involved in asexual reproduction?

A

1

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30
Q

As a result of asexual reproduction, are the offspring genetically identical or genetically unique?

A

Genetically identical

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31
Q

When fungi and plants reproduce asexually, which process do they use?

A

Mitosis

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32
Q

Do bacteria reproduce via sexual or asexual reproduction?

A

Asexual reproduction

33
Q

When bacteria reproduce asexually, which process do they use?

A

Binary fission

34
Q

What is another name for gametes?

A

Sex cells

35
Q

Examples of gametes

A
  • sperm
  • egg
36
Q

What does the term ‘haploid’ mean?

A

A cell that only has half the normal amount of genetic material

37
Q

Are gametes haploid cells?

A

Yes

38
Q

How many chromosomes does a human gamete have?

A

23

39
Q

When two haploid cells join, they form

A

A diploid cell

40
Q

During the process of meiosis, how many times does the cell divide?

A

2

41
Q

As a result of meiosis, how many cells are produced?

A

4

42
Q

Are the cells produced by meiosis genetically identical to each other, or genetically unique?

A

Genetically unique

43
Q

What is asexual reproduction

A
  • requires 1 parent
  • cells are replicated by mitosis to make genetically identical copies (or binary fission in bacteria)
  • The offspring are genetically identical to the parent and each other (clones)
  • It’s fast and very efficient —> so it works well in a constant environment
  • an example would be budding in hydra (grows on side and snaps off to grow elsewhere)
44
Q

What is the disadvantage of Asexual reproduction

A
  • All offspring are genetically identical, therefore a disease that affects one will affect them all
  • this also applies to other changes in environment (e.g. temp)
45
Q

What is sexual reproduction

A
  • each parent must make a gamete which contains half it’s genetic information
  • the gametes of both parents fuse during fertilisation to produce a zygote
  • the offspring are therefore a combination of the DNA of both parents - and are genetically different (unless they’re twins)
46
Q

Are there gametes in Asexual production and sexual production

A
  • Asexual production: no
  • sexual production: yes
47
Q

Does fertilisation take place in Asexual production and sexual production

A

Asexual production: no
sexual production: yes

48
Q

Is there variation between offspring in Asexual production and sexual production

A

Asexual production: No
sexual production: Yes

49
Q

What type of cell division is used in Asexual production and sexual production

A
  • Asexual production: Mitosis / Binary fission
  • sexual production: Meiosis
50
Q

Describe the process of Meiosis

A
  • first DNA is replicated
  • then the cell divides twice to produce 4 genetically different cells
  • each with half the parent genetic material
51
Q

Where does meiosis happen

A

Testes, ovaries

52
Q

Where does mitosis happen

A

Everywhere

53
Q

Describe the process of fertilisation

A
  • 300 million sperm enter vagina (many die trapped in folds or don’t get through cervix)
  • Pass through cervix
  • some are destroyed by phagocytes
  • about half go up the correct fallopian tube
  • they are activated by hormones and swim faster
  • sperm uses digestive enzymes to burrow into the egg
  • one sperm enters and the egg hardens to prevent other sperm getting in
  • The 23 chromosome from the male and female combine and make a diploid cell
54
Q

Advantages of sexual reproduction

A
  • offspring aren’t identical to parent (disease won’t wipe all of them out)
55
Q

Advantages of asexual reproduction

A
  • requires one parent
  • offspring are genetically identical to the parent (successful traits are passed on)
  • very fast in a constant environment
  • lots of offspring produced in less time
  • energy efficient
  • colonisation of local area where other organisms aren’t there
56
Q

Why is it important that gametes have only 23 chromosomes

A
  • prevents doubling of chromosome number
  • two can fertilise to restore back to original number of 46
57
Q

Where is DNA found

A

In nucleus of every cell in your body

58
Q

Where is DNA contained in the nucleus

A

In the chromosome (46 for humans/23 in human gametes)

59
Q

What is a gene

A
  • A section of DNA that codes for one protein
  • it is a sequence of bases that tell the cell how to make the protein.
60
Q

What is DNA made from

A

Nucleotides

61
Q

What is a mutation

A

Mutation is a change in the DNA sequence (e.g. one A might become a C)

62
Q

Describe the different types of mutation

A
  • Duplication (a base in the code occurs twice)
  • deletion (a base in the code goes away)
  • substitution ( a base gets replaced by another)
  • inversion (the sequence of bases switches around)
63
Q

explain how genetic disease happen

A
  • they are as a result of a mutation in a specific allele
  • they can be passed on from parent to offspring
64
Q

What is cystic fibrosis

A
  • it results in thickening of mucus in the airways and also in your gut which can result in problems breathing and in digestion
  • it affects cell membranes
  • it is caused by a recessive allele
65
Q

What is polydactyl

A
  • It is when an individual is born with extra fingers or toes
  • it is caused by a dominant allele
66
Q

What is amniocentesis

A
  • carried out at 15-16 weeks of pregnancy
  • a sample of the fluid surrounding the foetus is taken and the cells in it can be tested
67
Q

What is chronic villus sampling

A
  • carried out between 10-12 weeks of pregnancy
  • a sample is taken from the developing placenta and tested
68
Q

Pre-implantation sampling

A
  • some couples chose to use IVF and in this case the embryos can be screened for genetic disease before they are implanted
69
Q

Advantages and disadvantage of taking no action from genetic counselling

A
  • Adv: still a chance the baby doesn’t get it, no risk of harming baby
  • DAdv: baby still has a chance that it gets it , risk of damage to baby is still there but just not increased
70
Q

Advantages and disadvantage of pre natal diagnosis from chronic villus sampling and amniocentesis

A
  • Adv: able to get feral cells and determine disease, baby doesn’t feel it
  • DAdv: increases risk of miscarriage, faced with ethical decision to abort or not if baby gets the disease
71
Q

Advantages and disadvantage of IVF preimplantation screening

A

Adv: know if it has disease, the baby hasn’t started developing yet, no need for abortion (just don’t use it), not a natural pregnancy
DAdv: expensive

72
Q

Advantages and disadvantage of donor sperm / egg

A

Adv: disease
DAdv: baby can contact bio dad, the baby isn’t the dad’s bio baby, expensive

73
Q

Why is the human genome important

A
  • search for genes linked to different types of disease
  • understanding and treatment of inherited disorders
  • use in tracing human migration patterns from the past.
74
Q

What is the human genome

A
  • this is all off the genetic material found in a human
75
Q

What are the arguments for embryo screening

A
  • helps people stop suffering
  • treating disorders costs tax payers and government a lot of money
  • there’s laws to stop it going too far
76
Q

What are the arguments against embryo screening

A
  • implies people with genetic problems are undesirable —> lead to prejudice
  • could advance to people picking the most ‘desirable’ babies
  • expensive
77
Q

What is embryonic screening

A
  • In IVF, before putting embryo back you can take a cell and then analyse it for it’s genes
  • allowing you to detect genetic disorders
78
Q

What is the disadvantage to embryonic screening

A
  • embryos with ‘bad’ alleles are destroyed
  • it can lead to the decision to terminate pregnancy

Biology GCSE (38 decks)

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