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Biology IGCSE > Topic 17 > Flashcards

Topic 17 Flashcards

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1
Q

Chromosone

A

Made of DNA, which contains genetic information in the form of genes

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2
Q

Gene

A

A length of DNA that codes for specific protein -> controls our characteristics

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3
Q

Allele

A

Different versions of the same gene

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4
Q

Sex chromosones

A

Responsible for sex determination -> either labelled as X or Y

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5
Q

Sex chromosones -> males

A

X and Y chromosone (XY) -> Y chromosome causes male characteristics

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6
Q

Sex chromosones -> females

A

X and X chromosome (XY) -> XX combination causes female charactersitics

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7
Q

Sex chromosones -> sperm

A

Can carry either and X or Y chromosone so sex determination in humans depends on what chromosome is carried by speem that fertilises egg -> 50:50 chance of sperm carrying either chromosome

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8
Q

Haploid VS diploid cells -> haploid cell

A

Haploid nucleus: contains a single set of chromosones
-> 23 chromosomes
-> Example: gametes (sex cell)

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9
Q

Haploid VS diploid cells -> Diploid

A

Diploid nucleus: contains two sets of chromosomes -> there’s a pair of each type of chromosome (23 pairs/ 46 chromosomes)
-> Example humand body cells (except gametes)

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10
Q

Protein synthesis: DNA and genes

A

DNA strands contain bases which make up genes -> sequence of bases in a gene is the genetic code that determines the order (sequence) of amino acids in a protein
1. Each amino acid is coded for by a sequence of three bases in the gene
2. Amino acids are joined together to make specific proteins -> depending on order of gene’s bases
3. When a chain of amino acids has been assembled, it folds into a unique shape which allows protein to perform the task it’s meant to do -> different sequences of amino acids result in proteins with differenct shapes

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11
Q

DNA

A

Controls cell function by controlling production of proteins including enzymes, membrane carriers (carrier proteins) and neurotransmitter receptors

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12
Q

Protein production

A
  1. Gene coding for the protein remains in the nucleus
  2. Messanger RNA (mRNA) is a copy of a gene
  3. mRNA molecules are made in the nucleus and move to the cytoplasm
  4. mRNA passes through ribosomes
  5. Ribosome assembles amino acids into protein molecules
  6. The specific sequence of amino acids is determined by the sequence of bases in the mRNA
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13
Q

Body cells

A

Most body cells in an organsim have the same genes, but cells don’t express (make proteins from) all of their genes -> cells only express those genes that lead to the production of the specifi proteins they need to carry out their function

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14
Q

Mitosis

A

Nuclear division of a diploid cell that results inntwo genetically identical cells -> used in growth, cell replacement and repair of damaged tissues

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15
Q

Before mitosis happens

A

Cell’s chromosones are replicated -> end up with twice as many chromosones

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16
Q

During mitosis

A

Chromosones copies seperate and nucleus divides so one copy of each chromosone ends up in daughter cell -> mantains original chromosone number in each daughter cell

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17
Q

Stem cells

A

Unapecialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions

18
Q

Meiosis

A

A reduction division, which halves chromosome number from diploid to haploid (sperm + egg) forming four genetically different cells

19
Q

Monohybrid inheritance->Inheritance

A

Transmission of genetic information (DNA) between generations

20
Q

Monohybrid inheritance->Genotype

A

Alleles and organism has it’s genetic make-up) -> determines phenotype

21
Q

Monohybrid inheritance->Phenotype

A

Observable features of an organism

22
Q

Monohybrid inheritance->Homozygous

A

Having two identical alleles for a particular gene

23
Q

Monohybrid inheritance->Heterozygous

A

Having two different alleles for a particular gene

24
Q

Monohybrid inheritance->Dominant allele

A

Allele that’s always expressed if it’s present

25
Q

Monohybrid inheritance-> Recessive allele

A

Allele that’s only expressed when dominant version of allele isn’t present in orgnism’s genotype

26
Q

Monohybrid inheritance: Inheriting genes

A

Yo have two alleles of every gene in your body -> one from each parent
. Two identcial homozygous individuals that breed together will be pure-breeding -> can only pass one type of allele and so only one phenotype
. Heterozygous individual won’t be pure-breeding -> can pass on two different allels

27
Q

Dominant and recessive alleles

A

Dominant alleles (shown with capital letters) overrrule recessive alleles (shown with small letters)

28
Q

Dominant and recessive alleles: Displaying dominant characteristics

A

. Two dominant alleles
-> Example: CC
. One dominant and one recessive allele
-> Example: Cc

29
Q

Dominant and recessive alleles: displaying recessive characteristics

A

Both alleles must be recessive
-> Example: cc

30
Q

Genetic diagrams

A

Show the possible alleles of offspring and therefore probability of offspring having certain characteristics -> doesn’t tell exactly what will happen

31
Q

Genetic diagrams: monohybrid cross

A

When you cross two parents to look at just one characteristic

32
Q

Genetic diagrams: punnett square

A

Show genetic crosses

33
Q

Genetic diagrams: pedigree diagram

A

Shows how characteristics are inherited

34
Q

Carrier

A

Someone who doesn’t have the disorder but can pass it on

35
Q

Genetic diagrams: test crosses

A

Used to identify unknown genotypes by analysing ratio of phenotypes in specific offspring using genetic diagrams -> a homozygous recessive individual must be involved to do this

36
Q

Sex-linked genetic disorders: sex-linked characteristic

A

Feature that’s coded for by a gene located on a sex chromosone, making it more common in one sex than in the other -> Y chromosome is smaller than X chromosome and so carries fewer genes so most genes in sex chromosomes are only carried on X chromosome

37
Q

Sex-linked genetic disorders: male

A

Only have one X chromosome so often only have one allele for sex-linked genes so characteristic of this allele is shown eve; if it’s recessive -> makes men more likely than a woman to show recessive characteristics for genes that are sex linked

38
Q

Sex-linked genetic disorders

A

Disorders caused by faulty alleles located on sex chromosomes

39
Q

Blood type in humans

A

A, B, AB and O (phenotypes) -> gene for blood type in humans has three different alleles I^A, I^B and I^O (genotypes)

40
Q

Ineritance of blood groups: Codominance

A

Bothe alleles in heterozygous organism are expressed and so both determine the organism’s phenotype

Biology IGCSE (21 decks)

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