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Biology GCSE Edexcel > Topic 3- Genetics > Flashcards

Topic 3- Genetics Flashcards

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1
Q

Definition of sexual reproduction

A

Fertilisation of a female sex cell by a male sex cell

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2
Q

Definition of asexual reproduction

A

Producing clones

(offspring that are genetically identical to the parent)

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3
Q

Zygote

A
  • A fertilised egg cell

* A single cell made by the fertilisation of two gametes

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4
Q

Gamete

A

A sex cell produced by meiosis

Eg. Sperm, egg, pollen

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5
Q

Meiosis

A

Nuclear division that reduces the number of chromosomes by half

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6
Q

Chromosome

A

One molecule of DNA

For example in humans they’re in pairs, one from the mother and one from the father

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7
Q

DNA

Deoxyribonucleic acid

A

The genetic molecule

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8
Q

Haploid

A

• One set of a species chromosomes

Eg. Humans written as n=23

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9
Q

Diploid

A

The chromosomes come in pairs

Eg. Humans written as 2n=46

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10
Q

Genes

A

A section of DNA that makes a chromosome, that codes the instructions to make a protein

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11
Q

Proteins

A

Polymers of amino acids

Often an enzyme

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12
Q

Nucleotides

A

Basic building block of DNA

Made up of sugar,phosphate and nitrogenous base

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13
Q

Chromatin

A

Uncoiled chromosomes

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14
Q

Alleles

A

Different versions of a single gene

Eg. The gene for human eye colour has 2 alleles (brown and blue)

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15
Q

Parental phenotype

A

Characteristic of the parent

Eg. Purple flower for a pea plant

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16
Q

Parental genotype

A

Which alleles for the gene of the phenotype does the parent have

Eg. A parent pea plant with purple flowers may have a genotype of Rr

17
Q

How are dominant genotypes symbolised?

A

As a capital letter

Eg. Rr the capital R is the dominant genotype

18
Q

How are recessive genotypes symbolised?

A

With a lower case letter

Eg. Rr, the lower case R is the recessive genotype

19
Q

Homozygous

A

Has the same alleles

Eg. RR

20
Q

Heterozygote

A

Has different alleles

Eg.Rr

21
Q

Pure breeding

A

Means an individual has the same alleles for a gene

It is homozygous and has no genetic variation

22
Q

How many sex chromosomes does a human have?

A

1 pair of chromosomes are the sex chromosomes

23
Q

How many autosomes does a human have?

A

22 pairs are ordinary chromosomes called autosomes

24
Q

What are the different blood groups

A

A, B, AB or O

25
Q

Sex linked genetic disorder

A

Where the position of the gene that causes the disorder is on the sex chromosomes and is on the sex chromosomes region of the X chromosome that is absent on the y

26
Q

Example of a co dominant blood group

A

AB

27
Q

Harmful mutations

A

A change in the base sequence that stops the gene from being able to code for a functional protein (usaully an enzyme)

28
Q

A whole chromosome mutation

A

A section of chromosome is lost or is added to another chromosome

Eg. X and Y chromosome

29
Q

Muation

A

A mutation is a change in the sequence of a gene

30
Q

Where do mutations come from?

A

1) during the replication of DNA
2) UV damage, x-ray damage, gamma ray damage
3) mutagenic chemicals

31
Q

3 types of muation

A
  • neutral mutation (have no affect on phenotype)
  • harmful mutations
  • a whole chromosome mutation
32
Q

Stages of meiosis

A
  1. DNA is duplicated
    DIVISION 1
    -chromosomes line up in the centre of the cell
    -the pairs are pulled apart so each new cell only has one copy of each chromosome
    -each cell has a mixture of the mother’s and father’s chromosomes
    DIVISION 2
    -chromosomes line up in the centre again
    -chromatids are pulled apart

Biology GCSE Edexcel (9 decks)

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