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edexcel igcse biology > section e: inheritance and genetics > Flashcards

section e: inheritance and genetics Flashcards

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1
Q

dna def

A

the molecule that passes information from one generation to the next

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2
Q

what does dna stand for

A

deoxyribonucleic acid

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3
Q

gene def

A

small molecule of DNA that codes for a paticular protein

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4
Q

chromosome def

A

contains one double stranded dna molecule

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5
Q

genotype def

A

the alleles each cell has for a certain feature

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6
Q

phenotype def

A

the feature that results from the genotype

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7
Q

allele def

A

different forms of a gene

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8
Q

heterozygous def

A

genotypes with different allels of a gene

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9
Q

homozygous def

A

genotype with the same alleles of a gene

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10
Q

dominant def

A

this genotype will show its effect whether it is attached to a recessive allele or nto

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11
Q

recessive def

A

this genotype will only show its effect if there is no dominant allele present

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12
Q

diploid def

A

cells with homologous pairs of matching chromosomes

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13
Q

haploid def

A

cells with only half the normal diploid number of chromosomes

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14
Q

gamete def

A

male and female sex cells, formed by meiosis

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15
Q

F1 generation def

A

first generation of offspring

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16
Q

mitosis def

A

two cells are formed - these have the same number and type of chromosomes as the original cell.

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17
Q

meiosis

A

Four cells are formed - these only have half the number of chromosomes of the original cell. Forms gametes

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18
Q

mutation

A

Random events that occur in all organisms

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19
Q

homogolous pairs

A

Pairs of chromosomes that carry genes controlling the same features at the same positions on each chromosome. The members of each homologous pair are the same size and shape.

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20
Q

genome

A

The entire DNA of an organism

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21
Q

what copies the genetic code of DNA and then transfers the copy out of the nucleus to the cytoplasm

A

a different type of nucleic acid called ribonucleic acid, RNA

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22
Q

give three differences between DNA and RNA

A

dna contains a double helix, rna is a single strand
dna contains the sugar deoxyribose, rna contains ribose
rna contains the base Uracil instead of the base Thymine which is in dna

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23
Q

what does messenger RNA do

A

form a copy of the DNA code

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24
Q

what does transfer RNA do

A

carries amino acids to the ribosomes to make the protein

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25
Q

what are the two stages of protein synthesis

A

transcription and then translation

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26
Q

what is transcription

A

the DNA unwinds and unzips exposing the bases along the template strand. mRNA bases line up with the template strand according to the base pairing rules. the RNA nucleotides link up to form a mRNA molecule. when a section has been transcribed, the mRNA molecules leaves through pores in the nuclus and the DNA zips up again. because of the complementary base pairing the triplet code of the DNA is converted into a triplet code in the mRNA.

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27
Q

what is translation

A

the process of converting the code in the mRNA into a protein at the ribosomes. by this stage the code consists of sets of three bases in the mRNA (e.g. AUG, CCG) these triplets are codons and they code for a paticular amino acid. the mRNA molecule attaches to a ribosome, and the tRNA molecules (which have an anticodon of three base at one end complementary to a particular codon on the mRNA. at the other end is a site where a specific amino acid can attach. (one tRNA molecule for each type of amino acid). the tRNA molecule carries its amino acid to the ribosome, where its specific anticodon pairs up with the three bases of the corresponding mRNA codon. it starts at the start codon (always AUG) and stops at the stop codon.

28
Q

what is dna coiled around

A

proteins called histones

29
Q

which human cells don’t contain 46 chromosomes

A

red blood cells

gametes

30
Q

what is a zygote

A

when two nuclei of gametes join to form a single diploid cell

31
Q

what is the genome

A

the entire DNA of an organism

32
Q

phases of mitosis

A 
prophase
metaphase
anaphase
telophase
cytokenesis
33
Q

1st stage of mitosis

A

prophase. the DNA replicates and the chromosomes form two exact copies called chromatids. they are joined at a centromere. the nuclear membrane breaks down

34
Q

2nd stage of mitosis

A

metaphase. a structure called the spindle formed. the chromosomes line up in the middle centre of the spindle attached by their centromeres

35
Q

3rd stage of mitosis

A

anaphase. the spindle fibres shorten and pull the chromatids to opposite ends of the cell. the chromatids separate to become the chromosomes of the two daughter cells

36
Q

4th stage of mitosis

A

telophase. two new nuclei form at each pole of the cell. the cytoplasm starts to divide to produce two daughter cells. both daughter cells have a copy of each chromosome from the parent cell

37
Q

examples of where mitosis takes place

A

the skin
gut lining
red blood cells in the spleen
cancer cells

38
Q

types of blood

A

A
B
AB
O

39
Q

what is distinctive about type AB

A

it is the universal recipient:

can recieve blood from any type but cannot donate to any type

40
Q

what is distinctive about type O

A

universal doner.

can give blood to any type but can only receive blood from other type O’s

41
Q

what happens during cytokinesis

A

the cell splits in two

42
Q

where does mitosis occur

A

all over the body

43
Q

where does meiosis occur

A

sex organs

44
Q

number of divisions in mitosis

A

1

45
Q

number of divisions in meiosis

A

2

46
Q

what cells does mitosis create

A

all human cells except red blood cells and gametes

47
Q

what cells does meiosis create

A

gametes

48
Q

number of chromosomes in mitosis

A

46

49
Q

number of chromosomes in meiosis

A

23

50
Q

how many daughter cells does mitosis produce

A

2

51
Q

how many daughter cells does meiosis produce

A

4

52
Q

genetic makeup of daughter cell as compared to parent cells in mitosis

A

genetically identical

53
Q

genetic makeup of daughter cell as comapared to parent cells in meiosis

A

genetic variation

54
Q

genetic makeup of daughter cells as compared to other daughter cells in mitosis

A

genetically identical

55
Q

genetic makeup of daughter cells as compared to other daughter cells in meiosis

A

genetic variation

56
Q

function of mitosis

A

produce cells for growth and repair

57
Q

function of meiosis

A

produce gametes for reproduction

58
Q

where is a gene

A

on a chromosome

59
Q

how many copies of each chromosome and each gene are ther

A

two

60
Q

how many alleles are there of each gene

A

two

61
Q

classify the types of gene

A

dominant and recessive

62
Q

what is codominance

A

when there are genes with alleles that both contrubute to the phenotype, both alleles are expressed in the phenotype

63
Q

what is our sex determined by

A

the presence or absence of a Y chromosome

64
Q

what are the sex chromosomes

A

the X and Y chromosomes

65
Q

what chromosomes are there in all the cells of females (apart from the 44 non-sex chromosomes)

A

2 X chromosomes

66
Q

key principles of natural selection

A

there is variation within species
changinc onditions in the envrionment facours one paticular form of the species
the frequency of the favoured form increases
the frequency of the less well adapted form decreases under these conditions

edexcel igcse biology (5 decks)

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