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aqa gcse biology free > T6 reproduction > Flashcards

T6 reproduction Flashcards

1
Q

what is sexual reproduction

A

involves the production of gametes by meiosis

a gamete from each parent fuses to form a zygote

genetic information from each gamete is mixed so the resulting zygote is unique

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2
Q

what are gametes

A

sex cells (sperm and egg cells in animals, pollen and egg cells in flowering plants)

haploid (half the number of chromosomes)

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3
Q

what is meiosis

A

form of cell division involved in the formation of gametes in reproductive organs

chromosome number is halved

involves 2 divisions

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4
Q

what must occur prior to meiosis

A

interphase - copies of genetic information are made during this process

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5
Q

what happens during the first stage of meiosis

A

chromosome pairs line up along the cell equator

pair of chromosomes are separated and move to opposite poles of the cell

chromosome number is halved

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6
Q

what happens during the second stage of meiosis

A

chromosomes line up along the cell equator

chromatids are separated and move to opposite poles of the cell

four unique haploid gametes are produced

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7
Q

why is meiosis important for sexual reproduction

A

increases genetic variation

ensures that the zygote formed at fertilisation is diploid

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8
Q

describe fertilisation and its resulting outcome

A

gametes join together to restore the normal number of chromosomes and the new cell then divides by mitosis

as the embryo develops, cells differentiate

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9
Q

advantage of sexual reproduction

A

creates genetic variation in offspring, increasing chances of species adapting and surviving environmental changes

natural selection can be speeded up by humans in selective breeding to increase food production

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10
Q

disadvantages of sexual reproduction

A

two parents required making reproduction difficult in endangered populations or in species which have solitary lifestyles

more time and energy is required so fewer offspring are produced

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11
Q

what is asexual reproduction

A

involves mitosis only

produces genetically identical offspring known as daughter cells

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12
Q

advantages of asexual reproduction

A

1 parent required

lots of offspring produced quickly, enabling rapid colonisation of an area and reducing competition from other species

requires less energy and time as don’t need mate

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13
Q

disadvantage of asexual reproduction

A

no genetic variation reducing the chances of a species being able to adapt to environmental change

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14
Q

describe the circumstances in which malarial parasites reproduce sexually and asexually

A

sexual in mosquito

asexual in human host

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15
Q

describe the circumstances in which fungi and plants reproduce sexually and asexually

A

a - spores, seeds

s - to give variation, runner or bulb division

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16
Q

what is DNA

A

double-stranded polymer of nucleotides would to form a double helix

genetic material of the cell found in its nucleus

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17
Q

define genome

A

entire genetic material of an organism

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18
Q

why is understanding the human genome important

A

important for development of medicine

searching for genes linked to disease

understanding and treating inherited disorders

tracing human migration patterns from the past

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19
Q

what is a chromosome

A

long, coiled molecule of DNA that carries genetic information in the form of genes

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20
Q

define gene

A

small section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein

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21
Q

what are the monomers of DNA

A

nucleotides

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22
Q

what are DNA nucleotides made of

A

common sugar
phosphate group
A T C G

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23
Q

full names of the four bases in nucleotides

A

adenine
thymine
cytosine
guanine

24
Q

describe how nucleotides interact to form a molecule of DNA

A

sugar and phosphate molecules join to form a sugar-phosphate backbone in each DNA strand

base connected to each sugar

complementary base pairs joined by weak hydrogen bonds

25
explain how a gene codes for a protein
sequence of three bases in a gene forms a triplet each triplet codes for an amino acid order of amino acids determines the structure and function of protein formed
26
why is the folding of amino acids important in proteins such as enzymes
determines the shape of the active site which must be highly specific to the shape of its substrate
27
what is protein synthesis
formation of a protein from a gene
28
two stages of protein synthesis
transcription translation
29
what does transcription involve
formation of mRNA from a DNA template
30
outline transcription
DNA double helix unwinds RNA polymerase binds to a specific base sequence of non-coding DNA in front of a gene and moves along the DNA strand RNA polymerase joins free RNA nucleotides to complementary bases on the coding DNA strand mRNA formation complete, mRNA detaches and leaves the nucleus
31
what does translation involve
ribosome joins amino acids in a specific order dictated by mRNA to form a protein
32
outline translation
mRNA attaches to a ribosome ribosome reads the mRNA bases in triplets Each triplet codes for 1 amino acid which is brought to the ribosome by a tRNA molecule (carrier molecule) polypeptide chain is formed from the sequence of amino acids which join together
33
what is a mutation
random change in the base sequence of DNA which results mostly in no change to the protein coded for, or genetic variants of the protein occur continuously
34
describe the effect of a gene mutation in coding DNA
if a mutation changes the amino acid sequence, protein structure and function may change (enzyme may no longer fits its substrate binding site or a structural protein may lost its strength) if a mutation doesn't change amino acid sequence, there is no effect on protein structure or function
35
what is non-coding DNA
DNA which doesn't code for a protein but instead controls gene expression
36
describe the effect of a gene mutation in non-coding DNA
gene expression may be altered, affecting protein production and the resulting phenotype
37
what are alleles
different versions of the same gene
38
what is a dominant allele
version of a gene where only 1 copy is needed for it to be expressed
39
what is a recessive allele
version of a gene where 2 copies are needed for it to be expressed
40
what is meant when an organism is homozygous
when an organism has 2 copies of the same allele
41
what is meant when an organism is heterozygous
when an organism has 2 different versions of the same gene
42
what is the genotype
gene present for a trait
43
what is the phenotype
visible characteristic
44
problem with single gene crosses
most characteristics are controlled by multiple alleles rather than just one
45
what is an inherited disorder
disorder caused by the inheritance of certain alleles
46
how are embryos screened for inherited disorders
During IVF, one cell is removed and tested for disorder-causing alleles if the cell doesn't have any indicator alleles, then the originating embryo is implanted into the uterus
47
what are the ethical issues concerning embryo screening
could lead to beliefs in society that being disabled or having a disorder is less human or associated with inferiority destruction of embryos with inherited disorders is seen by some as murder as these would go on to become humans could be viewed as part of concept of designer babies as it may be for the parents convenience or wishes rather than child's wellbeing
48
what are the economic issues concerning embryo screening
costs of hospital treatment and medication will need to be considered if it is known that a child will have an inherited disorder and financial support explored if necessary
49
social issues concerning embryo screening
social care for children with IH may need to be considered if parents are unable to provide care if an embryo is found to have an IH and is terminated, this can prevent a child and its parents from potential suffering in the future due to the disorder
50
what is gene therapy
insertion of a normal allele into the cells of a person with an IH to functionally replace the faulty allele
51
ethical concerns surrounding gene therapy
going against and playing God introduced genes could enter sex cells and so be passed to future generations
52
sex chromosomes
M: XY F: XX
53
why does the inheritance of a Y chromosome mean that an embryo develops into a male
testes development in an embryo is stimulated by a gene present on the Y chromosome
54
what is a sex-linked characteristic
characteristic that is coded for by an allele found on a sex chromosome
55
why are men more likely to show the phenotype for a recessive sex-linked trait than women
many genes are found on X chromosome that have no counterpart on the Y chromosome women (XX) have 2 alleles for each sex-linked gene whereas men (XY) often only have 1 allele only 1 recessive allele is required to produce the recessive phenotype in males
56
why are the majority of genes found on the X chromosome rather than the Y chromosome
X chromosome is bigger than Y so more genes are carried on it

aqa gcse biology free (25 decks)

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