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biology > b13 - reproduction > Flashcards

b13 - reproduction Flashcards

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1
Q

how many chromosomes would you find in a human skin cell?

A

46

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2
Q

what does mitosis result in the formation of?

A

2 genetically identical daughter cells

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3
Q

difference between a gene and a chromosome?

A

chromosomes contain genes
gene is small section of DNA that codes for a specific protein/characteristic

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4
Q

by which process do bacterial cells divide?

A

binary fission

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5
Q

asexual reproduction

A

involves only one individual and the offspring is identical to the parent. there is no fusion of gametes or mixing of genetic information
- genes from one parent
- all clones to the parent - no variation
- only mitosis
- no gametes (sex cells) involved

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6
Q

sexual reproduction

A
  • involves the fusion of male and female gametes (fertilisation) producing genetic variation in the offspring
  • inherits a mixture of feature
  • egg (23) + sperm (23) > zygote > embryo
  • genes from two parents
  • gametes are formed by meiosis
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7
Q

meiosis

A

2 stage process of cell division that reduces the number of chromosomes of daughter cells, involved in making gametes for sexual reproduction
diploid (46) > haploid (23) > then copies itself to make 4 daughter cells (instead of 2 like mitosis)

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8
Q

examples of organism that go through asexual reproduction

A
  • strawberries
  • fungi
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9
Q

examples of organism that go through sexual reproduction

A
  • humans
  • insects
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10
Q

advantages of asexual reproduction

A
  • only one parent needed
  • many identical offspring reproduced
  • faster than sexual reproduction
  • already has the features required to survive in its environment
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11
Q

disadvantages of asexual reproduction

A
  • no variation
  • susceptible to environmental change
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12
Q

advantages of sexual reproduction

A
  • all offspring are different (variation)
  • survival advantage if environment changes
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13
Q

disadvantages of sexual reproduction

A
  • reliant on sperm and egg coming into contact
  • slower than asexual reproduction
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14
Q

gametes in flowering plants

A

pollen and egg cells

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15
Q

gametes in animals

A

sperm and egg cells

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16
Q

gametes

A

genetic information for organisms that reproduce sexually
- a haploid because it has one set of chromosomes
- haploid number 23 (half the number of what would be expected)

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17
Q

how is sperm adapted to its function?

A
  • mitochondria - gives it the energy to swim
  • acrosome - head of the sperm that has digestive enzymes that digests the outer layer of the egg
  • has a tail to swim streamlined
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18
Q

how is the egg adapted to its function

A
  • has a protective outer layer
  • is large so that it can be found by the sperm
  • releases chemicals to attract the sperm (a conc gradient)
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19
Q

diploid

A

has two sets of chromosomes (46)

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20
Q

why is it important that the number of chromosomes halves during meiosis

A
  • if it didn’t the embryo would have double the number of chromosomes - 92 instead of the normal 46
  • so that the number of chromosomes is conserved
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21
Q

fertilisation

A

when the games fuse to form a zygote.
the zygote then starts to divide through mitosis

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22
Q

why are mutations in sex cells more serious than mutations in body cells?

A
  • the mutation of a body cell can be easily solved by the body
  • however, if that happens with a sex cell and is then fertilised - it can then lead to genetic problems
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23
Q

mitosis vs meiosis

A
  • mitosis divides once but meiosis divides twice
  • 2 cells produced by mitosis and 4 cells produced by 4
  • mitosis has 46 chromosomes but meiosis has 23
  • mitosis is used for making body cells; meiosis is used for making gametes
  • mitosis happens in all parts of the body; meiosis happens only in the testes and ovaries
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24
Q

fungi

A
  • made up of a mass of thin threads called hyphae
  • the mass of the hyphae forms its visible structure of
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25
Q

reproduction in fungi

A
  • asexual
  • the fungi spores are produced by MITOSIS and they’re genetically identical to the parent
  • some fungi reproduce sexually in unfavourable conditions
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26
Q

toadstool

A

an asexual fruiting body that is full of spores

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27
Q

why does it produce sexually in unfavourable conditions?

A

so that variation can take place and the offspring can adapt to any changes in the environment

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28
Q

are fungi haploid or diploid most of the time?

A

haploid

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29
Q

when do two hyphae join together?

A

when environmental conditions are unfavourable

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30
Q

when do fungi undertake meiosis?

A

after two hyphae have joined together

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31
Q

sexual reproduction in fungi

A
  • some fungi reproduce sexually in unfavourable conditions. two hyphae from different fungi join and the nuclei fuse. so the new hypha has 2 sets of chromosomes
  • it then undergoes meiosis to make haploid spores which are different from the original hyphae
  • some of the spores may produce fungi better adapted to survive the adverse conditions
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32
Q

what type of pathogen is malaria?

A

protist

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33
Q

which two types of cells are targeted by malaria in humans?

A

liver cells and red blood cells

34
Q

where does fertilisation of malaria take place?

A

in the stomach of the mosquito

35
Q

where does the asexual reproduction of the malaria take place?

A

in the human host

36
Q

what are the effects of malaria in humans?

A

fever, loss of blood, brain damage, coma, death

37
Q

process of sexual production in the mosquito?

A
38
Q

process of asexual reproduction in the human host

A
39
Q

reproduction in plants

A
  • flowers are the sexual reproductive organs of plants
  • they make haploid gametes (pollen and egg cells) by meiosis that fuse to form diploid seeds that are genetically different to their parents
  • many plants can also reproduce asexually eg. strawberry plants and daffodil bulbs. this involves only mitosis so the offspring are genetically identical to the parent.
  • sexual reproduction is an advantage when flowers are destroyed or unfertilised
40
Q

what is DNA and its structure?

A
  • the molecule of inheritance - deoxyribonucleic acid
  • encodes and holds genetic instructions/code for different proteins
  • chromosomes and their genes are made of a molecule called DNA
  • each chromosome is a very long molecule called DNA
  • twisted ladder/ spiral shape = double helix
41
Q

DNA nucleotides

A
  • the backbone of the long strand of DNA is made of alternating sugar and phosphate molecules - attached to each sugar is one of four bases (A, T, C, G)
  • the combination of a sugar, phosphate and a base is a nucleotide
  • the DNA polymer is made of repeating nucleotide units/monomer
42
Q

DNA bases

A
  • the double helix ‘ladder’ of a DNA is held together by ‘rungs’ made from pairs of chemicals calls bases
  • four types of bases A>T, C>G
  • base pairs hold the two strands of the DNA helix together
  • the sequence of the bases along the DNA molecules form genetic code
43
Q

genomes

A
  • all the complete genetic information of an organism
  • includes all the chromosomes and the genetic material found in the mitochondria
  • has the ability to make many different proteins from the same gene by using it in different ways, or by switching part of a gene on or off
  • whole genome can now be sequenced in 24 hours
44
Q

which is larger a gene or a chromosome

A

a chromosome

45
Q

where in the cell is DNA produced to produce mRNA?

A

the nucleus

46
Q

what is an allele?

A

gene or combination of genes that we inherit from our parents eg.
H - straight hair, h - curly hair

47
Q

what is a genotype?

A

a combination of alleles that one has received from their parents - (Hh)
you can get different combinations - (hh) (HH) (Hh)

48
Q

what is a phenotype?

A

what the genotype codes for; the actual characteristics/ result of a genotype

49
Q

what is a dominant allele?

A

the capital letter - expressed in the phenotype

50
Q

what is a recessive allele?

A

the lower case letter - not expressed in the phenotype unless it is a double recessive gene (hh)

51
Q

genotype combinations EXAMPLE

A

straight hair = H
curly hair = h
(HH) - straight
(Hh) - straight
(hh) - curly - because double recessive gene

52
Q

homozygous

A

hh - same letter (homozygous recessive)
HH - same letter (homozygous dominant)

53
Q

heterozygous

A

different (letter) cases - Hh

54
Q

punnet square

A

a diagram used to calculate the probability of the phenotype being expressed

55
Q

examples of two genetically received diseases

A
  • CYSTIC FIBROSIS - must be a double recessive gene (both parents must have it for it to be dominant and the child to have it)
  • POLYDACTYLY - passed on by a dominant allele
56
Q

where in the cells are proteins made?

A

ribosomes

57
Q

what are some of the functions/uses of proteins in the body?

A
  • to make new cells when you grow, and to replace old or damaged cells
  • antibodies
  • enzymes
58
Q

what are proteins made up of?

A

amino acids

59
Q

examples of proteins:

A
  • ribosomes
  • antibodies
  • amylase
  • respiration enzyme
  • haemoglobin
60
Q

what is RNA?

A
  • has a single helix so that the bases can be read clearly during protein synthesis
  • has uracil as one of its bases instead of thymine
  • small section of DNA or gene that can eventually exit to the cytoplasm for protein synthesis
61
Q

explain the order of protein synthesis

A

1) genes in the DNA produce a template for the protein (a subsection not all of the DNA)
2) the template reflects the sequence of bases but is small enough to fit through the nuclear pore
3) the template (mRNA) binds to the ribosome surface
4) the carrier molecule, each attached to a specific amino acid attach themselves to the template in the order given by the DNA
5) the amino acids are joined together to form proteins
6) the carrier molecules keep bringing specific amino acids to add to the growing protein chain in the correct order until the template is completed
7) the protein detaches from the carrier molecules and the carrier molecules detach from the template and return to the cytoplasm to pick up more amino acids
8) the protein chain then folds up in to the unique shape of the protein

62
Q

how many bases code for an amino acid?

A

3

63
Q

what brings amino acids to ribosomes?

A

tRNA or carrier molecule

64
Q

why can’t DNA move into the cytoplasm?

A

the DNA is too big to move through the pores of the nucleus

65
Q

what might happen if there was a mistake in the DNA or if one of the bases were changed?

A

a mutation in the cells - the structure of the sequence of DNA is changed

66
Q

what is transcription?

A

making the mRNA or the template molecule from the DNA

67
Q

what is translation?

A

carrier molecule (tRNA) brings the amino acids to be joined to ribosomes

68
Q

what are simplified steps of protein synthesis?

A

DNA > transcripted > RNA > translated > protein

69
Q

what is a codon?

A

a triplet of three bases

70
Q

what does the amino acid on the tRNA depend on?

A

the three complementary bases attached to it

71
Q

what happens after the tRNA delivers its amino acid?

A

it then goes and attached to another cell to redo the process

72
Q

what is a non-coding region?

A

the parts of DNA in between the genes - involved in switching genes ‘on’ and ‘off’
when the gene is on it starts producing a protein

73
Q

what is a substitution?

A

when a base is swapped for another base - sometimes this might change the amino acid but other times it might not. this varies dependin on the amino acid

74
Q

what is an insertion?

A

if there is a change in sequence (the addition or deletion of a base) the whole protein will be different as it has different amino acids

75
Q

what are the effects of a mutation?

A

1) no change in amino acids or a slight change which doesn’t affect the protein structure
2) altered protein, so the protein may not work (eg. the active site of the substrate may no longer fit the substrate)
3) mutation within a non-coding region nearby to a gene may affect the expression (production) of a protein

76
Q

what happens if the mutation happens during mitosis?

A

it only affects a localised, isolated cells

77
Q

what happens if the mutation happens during meiosis?

A

affects the whole organism (their offspring)

78
Q

why does the mutation in meiosis affect the whole organism?

A
  • mitosis is only regarding a cell but meiosis involves the gametes
79
Q

what is sickle cell anaemia?

A
  • genetically inherited
  • one substitution in the haemoglobin, which changes the structure of the protein (in this case haemoglobin) so it can’t bind properly
80
Q

how do mutations affect genes?

A

1) protein may be unchanged - active site is the same shape so works normally
2) active site shape changed so the substrate does not fit and doesn’t work
3) active site changed shape so a different substrate fits - catalyses a different reaction

sometimes it can have a severe effect on the person but sometimes it may not

81
Q

are all mutations harmful?

A

no they’re not all harmful as some of them don’t change the structure of the protein therefore it doesn’t harm or affect the organism or some may be beneficial to the organism and allow them to adapt to survive eg. camouflage

82
Q

how does DNA control the synthesis of proteins in a cell?

A
  • the template (mRNA) is produced that reflects the sequence of bases in DNA of a single gene
  • the template is small enough to leave the nucleus through pores in the nuclear membrane, and bind to the surface of ribosome
  • carrier molecules (tRNA) in the cytoplasm, each attached to the a specific amino acid, attach themselves to the template in order given by the DNA until the template is completed
  • amino acids join together to form a specific protein
  • protein detaches from the carrier molecules , which detach from the template and return to cytoplasm to pick up more amino acids
  • once protein chain is complete the molecule folds up to form a unique shape that will enable it to carry out its functions in the cell

biology (7 decks)

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