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biology gcse > ❤️‍🔥3- inheritance > Flashcards

❤️‍🔥3- inheritance Flashcards

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1
Q

genome

A

the entire set of the genetic material of an organism

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2
Q

each gene within a genome

A

is made up of a small section of DNA that codes for a particular sequence of amino acids- these sequences form different types of proteins

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3
Q

having two alleles the same is called

A

homozygous

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4
Q

having two alleles which are different are called

A

heterozygous

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5
Q

genes control

A

our characteristics as they code for proteins that play important roles in what our cells do

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6
Q

in the nucleus of a cell, the DNA

A

double helix supercoils to form structures called chromosomes- they are only visible through cell division

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7
Q

human body cells contain __ chromosomes

A

23 pairs of chromosomes

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8
Q

one chromosome from a pair is

A

inherited from each parent

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9
Q

each chromosome pair is called

A

a homologous pair

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10
Q

the 23rd pair of chromosomes are

A

the sex chromosomes

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11
Q

in females the sex chromosomes are

A

the same- a homozygous genotype (XX)

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12
Q

in males the sex chromosomes are

A

different- a heterozygous genotype (XY)

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13
Q

how many chromosomes do gametes contain

A

23 individual chromosomes

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14
Q

haploid

A

23 chromosomes

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15
Q

diploid

A

23 pairs of chromosomes

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16
Q

a gene is

A

a short length of DNA found on a chromosome that codes for a particular characteristic

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17
Q

alleles are

A

variations of the same gene- As we have two copies of each chromosome, we have two copies of each gene and therefore two alleles for each gene
One of the alleles is inherited from the mother and the other from the father
This means that the alleles do not have to ‘say’ the same thing

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18
Q

alleles can be

A

dominant or recessive- A dominant allele only needs to be inherited from one parent in order for the characteristic to show up in the phenotype
A recessive allele needs to be inherited from both parents in order for the characteristic to show up in the phenotype.
If there is only one recessive allele, it will remain hidden and the dominant characteristic will show

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19
Q

gamete

A

sex cells

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20
Q

chromosome

A

threads which carry genetic information in the form of genes- located in the nucleus of cells

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21
Q

gene

A

short lengths of DNA found on chromosomes which code for specific proteins

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22
Q

allele

A

alleles are different versions of a particular gene

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23
Q

dominant

A

a dominant allele is always expressed, even if only one copy is present

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24
Q

recessive

A

a recessive allele is only expressed if two copies are present (therefore no dominant allele present)

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25
Q

homozygous

A

if two alleles of a gene are the same

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26
Q

heterozygous

A

if two alleles of a gene are different

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27
Q

genotype

A

the combination of alleles that control each characteristic

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28
Q

phenotype

A

the observable characteristics of an organism

29
Q

who is responsible for determining the sex of a child

A

the male as only he has a Y chromosome

30
Q

characteristics which are controlled by more then one gene are described as

A

polygenic

31
Q

mitosis is used for

A

growth, repair of damaged tissues, replacement of cells and asexual reproduction

32
Q

process of mitosis

A

Just before mitosis, each chromosome in the nucleus copies itself exactly (forms x-shaped chromosomes)
Chromosomes line up along the centre of the cell where cell fibers pull them apart
The cell divides into two; each new cell has a copy of each of the chromosomes

33
Q

importance of mitosis

A

All cells in the body (excluding gametes) are produced by mitosis of the zygote
Mitosis is important for replacing cells e.g, skin cells, red blood cells and for allowing growth (production of new cells e.g. when a zygote divides to form an embryo)

34
Q

mitosis

A

Mitosis is cell division which produces two identical diploid cells for growth and repair

35
Q

meiosis

A

Meiosis is the type of cell division that produces gamete

36
Q

when gametes are formed chromosomes must be

A

halved - otherwise there would be double the number of chromosomes after they join at fertilisation in the zygote

37
Q

when does the halving of chromosomes occur

A

during meiosis, as so it is described as a reduction division in which the chromosome number is halved from diploid to haploid, resulting in genetically different cells

38
Q

process of meiosis

A

Each chromosome makes identical copies of itself (forming X-shaped chromosomes)
First division: chromosomes pair up along the centre of the cell, recombination occurs and then cell fibres will pull the pairs apart, each new cell will have one of each recombinant chromosome pair
Second division: chromosomes will line up along the centre of the cell, cell fibres will pull them apart (as with mitosis)
A total of four haploid daughter cells will be produced

39
Q

importance of meiosis

A

Production of gametes e.g. sperm cells and egg cells, pollen grains and ovum
Increases genetic variation of offspring
Meiosis produces variation by forming new combinations of maternal and paternal chromosomes every time a gamete is made, meaning that when gametes fuse randomly at fertilisation, each offspring will be different from any others

40
Q

features of mitosis

A

two daughter cells produced, daughter cells are diploid, daughter cells are genetically identical to each other and to the parent cell, one cell division occurs

41
Q

features of meiosis

A

four daughter cells produced, daughter cells are haploid, daughter cells are genetically different from each other and the parent cell, two cell divisions occur

42
Q

variation

A

differences between individuals of the same species

43
Q

variation can be dividing into two types depending on

A

how you are able to group the measurements

44
Q

two types of variation

A

-Continuous variation is when there are very many small degrees of difference for a particular characteristic between individuals and they are arranged in order and can usually be measured on a scale
Examples include height, mass, finger length etc. where there can be many ‘in-between groups
-Discontinuous variation is when there are distinct differences for a characteristic
For example, people are either blood group A, B, AB or O; are either male or female; can either roll their tongue or not - there are no ‘in-betweens’

45
Q

phenotypic variation can be caused in two main ways:

A

environmental- caused entirely by the environment in which the organism lives
genetic- controlled entirely by genes

46
Q

meiosis creates

A

genetic variation between the gametes produced by an individual - this means each gamete carries substantially different alleles

47
Q

during fertilisation any

A

male gamete can fuse with any female gamete to form a zygote - this random fusion of gametes at fertilisation creates genetic variation between zygotes as each will have a unique combination of alleles

48
Q

characteristics of all species can be affected by environmental factors such as

A

climate, diet, accidents, culture and lifestyle

49
Q

discontinuous variation is usually caused by

A

genetic variation alone

50
Q

mutations are

A

rare, random changes that occur in the sequence of DNA bases in a gene or a chromosome

51
Q

mutations occur

A

continuously

52
Q

mutations in a gene can lead to

A

a change in the protein that the gene codes for

53
Q

most mutations don’t alter the protein or

A

only alter it slightly so that its appearance or function isn’t changed

54
Q

an insertion mutation

A

changes the amino acid that would have been coded for by the group of three bases in which the mutation occurs

55
Q

an insertion mutation also has a knock on

A

effect by changing the groups of three bases further on in the DNA sequence

56
Q

a deletion mutation

A

changes the amino acid that would have been coded for by the group of three bases in which mutation occurs

57
Q

a deletion mutation has a knock on

A

effect by changing the groups of three bases further on in the DNA sequence

58
Q

a substitution mutation

A

will only change the amino acid for the group of three bases in which the mutation occurs- it will not have a knock on effect

59
Q

evolution is

A

the change in the frequency of a phenotype in a population over many generations

60
Q

Darwins theory

A

Individuals in a species show a wide range of variation caused by differences in genes
Individuals with characteristics most suited to the environment have a higher chance of survival and more chances to reproduce
Therefore these characteristics are passed to their offspring at a higher rate than those with characteristics less suited to survival
Over many generations, these beneficial characteristics become more common in the population and the species changes (the species evolves)

61
Q

antibiotics are

A

chemical substances made by certain fungi or bacteria that affect the working of bacterial cells either by disrupting their structure or function or by preventing them from reproducing

62
Q

antibodies are effective

A

against bacteria but not against viruses

63
Q

antibiotics target processes and structures that are

A

specific to bacteria cells- as such they do not generally harm animal cells

64
Q

antibiotics have been

A

overused and antibiotic resistance has developed in many different types of bacterial species

65
Q

bacteria resistance to antibiotics

A

Bacteria, like all organisms, have random mutations in their DNA
One of these mutations may give them resistance to an antibiotic
If an organism is infected with bacteria and some of them have resistance, they are likely to survive treatment with antibiotics
The population of the resistant bacteria will increase
If the resistant strain is causing a serious infection then another antibiotic will be needed
A strain of Staphylococcus aureus has developed resistance to a powerful antibiotic methicillin, this is known as MRSA (Methicillin resistant Staphylococcus aureus)
MRSA can infect wounds and is difficult to treat without antibiotics

66
Q

preventing resistant bacteria

A

Doctors need to avoid the overuse of antibiotics, prescribing them only when needed – they may test the bacteria first to make sure that they prescribe the correct antibiotic
Antibiotics shouldn’t be used in non-serious infections that the immune system will ‘clear up’
Antibiotics shouldn’t be used for viral infections
Patients need to finish the whole course of antibiotics so that all the bacteria are killed and none are left to mutate to resistant strains
Antibiotics use should be reduced in industries such as agriculture – controls are now in place to limit their use in farming

67
Q

reducing the spread of resistant strains of bacteria

A

Good hygiene practices such as handwashing and the use of hand sanitisers have reduced the rates of resistant strains of bacteria, such as MRSA, in hospitals
The isolation of infected patients to prevent the spread of resistant strains, in particular in surgical wards where MRSA can infect surgical wounds

68
Q

antibiotics do not affect viruses-

A

Viruses cannot be treated with antibiotics
This is because antibiotics work by disrupting cell functions such as respiration, or breaking down the structure of the cell in some way
However, viruses do not carry out any cell functions and do not have cell walls, cell membranes or any cell organelles as viruses infect and utilise the machinery of animal cells to reproduce, which are not affected by antibiotics.
Therefore the action of antibiotics do not affect them

biology gcse (13 decks)

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