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GCSE Biology > Story of Us : part 1 > Flashcards

Story of Us : part 1 Flashcards

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1
Q

what is the full form of DNA?

A

deoxyribonucleic acid

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2
Q

what is the function of DNA?

A
  • stores the genetic information
  • controls cell activities
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3
Q

what is genetic information comprised of?

A
  • instructions for building all proteins within an organism
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4
Q

how is DNA found in eukaryotes?

A
  • within the nucleus
  • as linear (straight) chromosomes
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5
Q

how is DNA found in prokaryotes?

A
  • in the cytoplasm
  • in the form of a circular chromosome and many small plasmids
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6
Q

what is the structure of DNA?

A
  • double helix shape (two strands wrapping around each other)
  • made up of building blocks called nucleotides
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7
Q

what are nucleotides comprised of?

A
  • a sugar (deoxyribose)
  • a phosphate
  • a nitrogenous base
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8
Q

what are the four types of base and its pairs?

A
  • adenine - thymine
  • cytosine - guanine
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9
Q

how are the nucleotides joined together?

A
  • by covalent bonds between the sugar of one nucleotide and the phosphate group of the next nucleotide - forming the sugar phosphate backbone
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10
Q

what will always be the same for the bases?

A
  • the number of A’s and T’s
  • the number of C’s and G’s
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11
Q

what is RNA?

A
  • a type of nucleic acid called ribonucleic acid
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12
Q

what is the structure of RNA?

A
  • the RNA nucleotides are joined to form a single strand
  • the nucleotides are joined by a covalent bond between the sugar of one nucleotide and the phosphate of the next
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13
Q

how does RNA differ from DNA?

A
  • RNA is single stranded while DNA is double stranded
  • RNA has a sugar called ribose while DNA has a sugar called deoxyribose
  • RNA has the base uracil (U) while DNA has the base thymine (T)
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14
Q

what are the two types of RNA you need to know?

A
  • messenger RNA
  • transfer RNA
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15
Q

describe the messenger RNA.

A
  • mRNA
  • formed in the nucleus of the cell
  • it copies the sequence of bases of a section of DNA in a process called transcription
  • mRNA carries the code for building a specific protein from the nucleus to the ribosomes in the cytoplasm
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16
Q

describe the transfer RNA.

A
  • tRNA
  • found in the cytoplasm
  • the tRNA picks up specific amino acids from the cytoplasm and brings them into position on the surface of a ribosome where they can be joined together in specific order to make a specific protein
  • process is called translation
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17
Q

what is a gene?

A
  • a length of DNA which codes for a protein
  • this means it provides info on the sequence of amino acids in a protein (like an enzyme)
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18
Q

what do the proteins coded by genes do?

A
  • these proteins then control chemical reactions, growth, colouration and all inheritable characteristics
  • this is why a gene codes for a characteristic
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19
Q

how are the codes for the proteins read?

A
  • universally
  • the code is universal
  • bacteria read it in the same way that animal cells and plant cells read it
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20
Q

in DNA, what do the sequence of three bases code for?

A
  • a specific amino acid
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21
Q

what do we refer to every three bases as in a chain of amino acids in a protein?

A
  • a codon
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22
Q

what is DNA wrapped in?

A
  • structures called chromosomes
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23
Q

how many of each chromosome does a person have?

A
  • two of each chromosome
  • one of each pair comes from the father, the other from the mother
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24
Q

why do we say chromosomes are homologous?

A
  • genes controlling a specific characteristic are situated at the same point on each chromosome
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25
Q

what is there in every diploid nucleus?

A
  • there is a pair of genes for each characteristic
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26
Q

what can genes have?

A
  • different versions called alleles, which code for different forms of a protein
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27
Q

what is the genome?

A
  • one copy of all an organism’s DNA
  • in humans this is all the DNA that makes up the 23 pairs of chromosomes found in all diploid body cells
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28
Q

what are all the diploid body cells?

A
  • all cells except sex cells or gametes which only have half of a person’s genome (haploid)
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29
Q

how many chromosomes do human body cells contain?

A
  • two copies of each of their 23 chromosomes, this is a diploid cell
  • some cells (and organisms) only contain one copy of each chromosome - they are called haploid
30
Q

which is the “sex” chromosome?

A
  • the 23rd chromosome
  • it determines your sex
  • if you have two X chromosomes you are biologically female, if you have 1 X and 1 Y you are biologically male
31
Q

which cells are haploid?

A
  • human gametes
  • this is so, when they fuse, they can form a diploid offspring
32
Q

what does growth and reproduction require?

A
  • cell division
33
Q

what are the two types of cell division?

A
  • mitosis and meiosis
34
Q

what does the cell division of mitosis produce?

A
  • genetically identical daughter cells which are diploid - they have one pair of each chromosome in each nucleus
  • mitosis is used for growth, repair and asexual reproduction
35
Q

what does the cell division of meiosis produce?

A
  • produces haploid gametes (sperm, eggs, pollen) which are not genetically identical
  • meiosis is only used to produce gametes for sexual reproduction
36
Q

what is variation in offspring produced by?

A
  • genetic variation in gametes produced by meiosis
  • random fertilisation of ova (egg cells) by male gametes
37
Q

what is important in order for evolution to occur?

A
  • variation
38
Q

what type of characteristic is variation?

A
  • can be genetic, environmental or a combination of both
39
Q

genetic characteristics

A
  • following sexual reproduction, or mutation, organisms will have different versions of genes to another individual
40
Q

environmental characteristics

A
  • the environment might also affect the characteristics of an organism
41
Q

both genetic and environmental characteristics

A
  • usually both genetic and environmental factors contribute to the variation found in individuals of a species
42
Q

what are the two main types of variation?

A
  • continuous and discontinuous
43
Q

continuous variation

A
  • e.g. height, where there is a smooth range of measurements
44
Q

discontinuous variation

A
  • e.g. blood group, where there are distinct categories with no values in between
45
Q

which type of variation is more heavily influenced by environmental factors?

A
  • continuous variation
46
Q

who was Gregor Mendel?

A
  • in 1860, an austrian monk called gregor mendel noticed that the peas in the kitchen were two types, tall and dwarf
  • he allowed the tall ones to self-pollinate (reproduce with themselves) for a number of generations and did the same with the dwarf ones
  • he then assumed that both types were pure breeding
  • he then crossed (bred) a tall pea plant with a dwarf pea plant
47
Q

what does pure breeding mean?

A
  • a group of identical individuals that always produce offspring of the same type when bred
48
Q

what was gregor mendel’s method?

A
  1. he opened up the flowers of the tall plants when they were just emerging and cut out
    the stamens, the male reproductive parts.
  2. This would stop the pea plant from self-pollinating.
  3. He then covered the rest of the flower with a bag to stop insects pollinating the carpel,
    the female part, with pollen from an unknown source.
  4. When the flowers from a dwarf variety were ready he removed some pollen from one of
    the stamens with a very fine paintbrush and brushed it onto the stigma of a carpel
    protected by the bag.
49
Q

what were the results of gregor medel’s experiment?

A
  • the flower produced seeds and when these had dried out properly he planted them to see what was produced
  • all of the seeds grew into tall plants, even though half the parents were dwarf plants
  • he allowed these plants to self-pollinate, i.e. one plant acting as both parents
  • surprisingly, tall parents gave rise to some dwarf plants
  • when the offspring were counted he found that 839 were tall and 276 were dwarf
  • he realised that this was a ratio of about 3 tall plants to 1 dwarf
50
Q

label the flower.

A

onenote pictures

51
Q

what is an allele?

A
  • a version of a gene
52
Q

what do the genes found on the chromosomes have?

A
  • two different forms - called alleles
53
Q

what sort of alleles will pure breeding plants have?

A
  • only have alleles for one type - e.g. tall or dwarf
54
Q

what are the two types of allele?

A
  • dominant or recessive
55
Q

what is a dominant allele?

A
  • only needs one allele present to be expressed
56
Q

what is a recessive allele?

A
  • needs two alleles to be present to be expressed
57
Q

what does heterozygous dominant alleles mean?

A
  • one is recessive and the other is dominant
  • the dominant allele overpowers the recessive allele
58
Q

what does homozygous dominant alleles mean?

A
  • two uppercase alleles
  • the dominant allele overpowers
59
Q

what does heterozygous recessive alleles mean?

A
  • one dominant allele and one recessive
  • the recessive allele overpowers the dominant allele
60
Q

what does homozygous recessive alleles mean?

A
  • both the same type of allele (lowercase)
  • the recessive allele overpowers
61
Q

fill in a punnet square to cross a Tt and Tt.

A
62
Q

what is a genotype?

A
  • a combination of alleles e.g. TT or Tt
63
Q

what is a phenotype?

A
  • what is expressed e.g. tall or dward
64
Q

what are the punnett square rules?

A
  • use one letter to represent a gene
  • use the upper case to represent the dominant allele and the lower case to represent the recessive allele
  • write the genotypes (allele combination) and phenotypes (characteristic of the parents
  • write the alleles found in each gamete (separately to the parents’ genotypes)
  • write the genotype and phenotype of each offspring
  • finish with the probability of each phenotype in the offspring (fraction/% or ratio )
65
Q

what is polygenic inheritance?

A
  • where many characteristics are controlled by several genes which influence each other
  • these characteristics are more likely to show continuous variation, e.g. skin colour in humans
66
Q

what is cystic fibrosis?

A
  • a disease that effects the lungs
  • it affects the CFTR protein which causes mucus to be incredibly thick, so thick that it cannot be removed from the lungs
67
Q

how much can cystic fibrosis reduce your life expectancy by?

A
  • up to 30 years
68
Q

is there a cure for cystic fibrosis?

A

no

69
Q

is the cystic fibrosis gene dominant or recessive?

A
  • recessive
  • the heterozygous parents do not have the disease but do carry an allele - we refer to them as carriers
70
Q

what is codominance?

A
  • where both alleles are expressed and both take part in the characteristic
71
Q

what can be used to determine the probability of inheriting a genetic disease?

A
  • family trees/pedigree diagrams
72
Q

show the likelihood of having a boy or a girl.

A

50:50

GCSE Biology (29 decks)

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