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17. Inheritance Flashcards

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1
Q

What is inheritance?

A

Inheritance is the transmission of genetic information from generation to generation

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2
Q

Where are chromosomes located?

A

Chromosomes are located in the nucleus of cells

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3
Q

What are chromosomes?

A

They are thread-like structures of DNA, carrying genetic information in the form of genes

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4
Q

What is a gene?

A

A gene is a short length of DNA found on a chromosome that codes for a specific protein (characteristic)

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5
Q

What is an example of a gene?

A

This could be a structural protein such as collagen found in skin cells, an enzyme or a hormone

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6
Q

What do genes control?

A

Genes control our characteristics

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7
Q

How do genes control our characteristics?

A

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

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8
Q

What is an allele?

A

Alleles are different versions of a particular gene

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9
Q

How many DIFFERENT chromosomes do humans have?

A

All humans have 23 different chromosomes in each cell

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10
Q

How many chromosomes do people have in general?

A

In most body cells, we have 2 copies of each chromosome, leading to a total of 46 chromosomes

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11
Q

What cells are an exception to having 46 chromosomes? How many do they have?

A

The gametes (egg and sperm cells) only have one copy of each chromosome, meaning they have a total of 23 chromosomes in each cell

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12
Q

What does it mean if a cell has a DIPLOID NUCLEI?

A

Nuclei with two sets of chromosomes are known as diploid nuclei

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13
Q

What does it mean if a cell has a HAPLOID NUCLEI?

A

Nuclei with one set of unpaired chromosomes are known as haploid nuclei

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14
Q

What is sex determined by?

A

Sex is determined by an entire chromosome pair (as opposed to most other characteristics that are just determined by one or a number of genes)

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15
Q

What sex chromosomes do females have?

A

XX

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16
Q

What sex chromosomes do males have?

A

XY

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17
Q

Who is responsible for determining the sex of the child?

A

As only a father can pass on a Y chromosome, he is responsible for determining the sex of the child

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18
Q

How can you show the inheritance of sex?

A

The inheritance of sex can be shown using a genetic diagram (known as a Punnett square)

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19
Q

What is different between a genetic diagram for sex inheritance and inheritance of other features?

A

the X and Y chromosomes taking the place of the alleles usually written in the boxes

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20
Q

What happens before a cell divides?

A

When cells divide their chromosomes double beforehand

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21
Q

Why do the chromosomes in a cell double before cell division?

A

This ensures that when the cell splits in two, each new cell still has two copies of each chromosome (is still diploid)

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22
Q

When is mitosis used?

A

This type of cell division is used for growth, repair of damaged tissues, replacement of cells and asexual reproduction

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23
Q

What is the definition of mitosis?

A

Mitosis is defined as nuclear division giving rise to genetically identical cells

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24
Q
  1. What is the first step to prepare for mitosis?
A

Just before mitosis, each chromosome in the nucleus copies itself exactly (forms x – shaped chromosomes)

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25
Q
  1. What happens after the chromosomes double before mitosis?
A

Chromosomes line up along the centre of the cell

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26
Q
  1. What happens to the chromosomes once they line up along the centre of the cell?
A

cell fibres pull them apart

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27
Q

What happens once the cell fibres pull the chromosomes apart?

A

The cell divides into two; each new cell has a copy of each of the chromosomes

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28
Q

Why is mitosis so important?

A

All cells in the body (excluding gametes) are produced by mitosis of the zygote

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29
Q

What does mitosis replace?

A

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)

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30
Q

What 3 processes does mitosis occur in?

A

Growth
Repair
Asexual reproduction

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31
Q

How does mitosis help in growth?

A

mitosis produces new cells

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32
Q

How does mitosis help in repair?

A

to replace damaged or dead cells

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33
Q

How does mitosis help in asexual reproduction?

A

mitosis produces offspring that are genetically identical to the parent

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34
Q

What do all tissues in the human body contain?

A

Many tissues in the human body contain a small number of unspecialised cells

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35
Q

What are unspecialised cells called?

A

These are called stem cells

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36
Q

What is the function of stem cells?

A

their function is to divide by mitosis and produce new daughter cells that can become specialised within the tissue and be used for different functions

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37
Q

What type of cells does meiosis produce?

A

Meiosis is a type of nuclear division that gives rise to cells that are genetically different

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38
Q

What is meiosis used to produce?

A

It is used to produce the gametes (sex cells)

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39
Q

What must

meiosis result in?

A

The number of chromosomes must be halved when the gametes (sex cells) are formed

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40
Q

Why must the number of chromosomes be halved before meiosis?

A

Otherwise there would be double the number of chromosomes after they join at fertilisation in the zygote (fertilised egg)

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41
Q

What is meiosis described as?

A

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

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42
Q
  1. What happens at the beginning of meiosis?
A

It starts with chromosomes doubling themselves as in mitosis and lining up in the centre of the cell

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43
Q
  1. What happens after the chromosomes have lined up?
A

recombination occurs and then cell fibres will pull the pairs apart, each new cell will have one of each recombinant chromosome pair

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44
Q
  1. What happens in the second division?
A

chromosomes will line up along the centre of the cell, cell fibres will pull them apart (as with mitosis)

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45
Q

How many cells does meiosis form and how can they be described?

A

Because of this double division, meiosis produces four haploid cells

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46
Q

What are examples of cells produced by meiosis?

A

Production of gametes e.g. sperm cells and egg cells, pollen grains and ovum

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47
Q

What does meiosis help with?

A

Increases genetic variation of offspring

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48
Q

How does meiosis increase genetic variation?

A

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

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49
Q

What is the difference between mitosis and meiosis in the number of cells produced?

A

MI - two cells produced (known as daughter cells)

ME - four cells produced (known as daughter cells)

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50
Q

What is the difference between mitosis and meiosis in the daughter cells?

A

MI - diploid

ME - haploid

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51
Q

What is the difference between mitosis and meiosis in the genetic differentiation of the daughter cells?

A

MI - genetically identical to each other and to the parent cell
ME - genetically different from each other and the parent cell

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52
Q

What is the difference between mitosis and meiosis in the number of divisions?

A

MI - one cell division occurs

ME - two cell division occurs

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53
Q

How many copies of each chromosome do we have?

A

2

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54
Q

How many copies do we have of each gene?

A

2 copies

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55
Q

How many copies do we have of each allele (for each gene)?

A

2

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56
Q

Why do we have 2 different alleles?

A

One of the alleles is inherited from the mother and the other from the father

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57
Q

What is a phenotype?

A

The observable characteristics of an organism (seen just by looking – like eye colour, or found – like blood type) is called the phenotype

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58
Q

What is a genotype?

A

The combination of alleles that control each characteristic is called the genotype

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59
Q

What 2 types of allele can there be?

A

Alleles can be dominant or recessive

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60
Q

What is the difference between recessive and dominant alleles in relation to the phenotype?

A

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.

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61
Q

What happens if there is only one recessive allele?

A

If there is only one recessive allele, it will remain hidden and the dominant characteristic will show

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62
Q

What does it mean if a person is homozygous?

A

If the two alleles of a gene are the same, we describe the individual as being homozygous

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63
Q

What two different types of homozygous can a person be?

A

homozygous recessive

homozygous dominant

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64
Q

What does it mean if a person is homozygous recessive?

A

having two copies of the recessive allele

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65
Q

What does it mean if a person is homozygous dominant?

A

having two copies of the dominant allele

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66
Q

What does it mean if a person is heterozygous?

A

If the two alleles of a gene are different, we describe the individual as being heterozygous

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67
Q

What letter represents a dominant and recessive allele in a genetic diagram?

A

The dominant allele is given a capital letter and the recessive allele is given the same letter, but lower case

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68
Q

Can we tell the genotype from a person’s phenotype?

A

We cannot always tell the genotype of an individual for a particular characteristic just by looking at the phenotype

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69
Q

Why can’t we always tell a persons genotype from the phenotype?

A

a phenotype associated with a dominant allele will be seen in both a dominant homozygous and a dominant heterozygous genotype

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70
Q

What offspring will be produced if identically homozygous individual reproduce?

A

If two individuals who are both identically homozygous for a particular characteristic are bred together, they will produce offspring with exactly the same genotype and phenotype as the parents

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71
Q

Why is crossing two homozygous individuals called pure-breeding?

A

We describe them as being ‘pure breeding’ as they will always produce offspring with the same characteristics

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72
Q

Can heterozygous individuals participate in pure breeding?

A

A heterozygous individual can pass on different alleles for the same characteristic each time it is bred with any other individual and can therefore produce offspring with a different genotype and phenotype than the parents – as such, heterozygous individuals are NOT pure breeding

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73
Q

What is a monohybrid inheritance?

A

Monohybrid inheritance is the inheritance of characteristics controlled by a single gene (mono = one)

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74
Q

What does a punnett square show?

A

A Punnett square diagram shows the possible combinations of alleles that could be produced in the offspring

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75
Q

What is the ratio D to R when two heterozygous individuals are crossed?

A

There is more variation in this cross, with a 3:1 ratio of tall : short, meaning each offspring has a 75% chance of being dominant and a 25% chance of being recessive

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76
Q

What is the ratio D to R when one homozygous recessive individual and one heterozygous individual are crossed?

A

In this cross, there is a 1:1 ratio of dominant to recessive, meaning a 50% chance of the offspring being dominant and a 50% chance of the offspring being recessive

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77
Q

How can you find an unknown genotype?

A

Breeders can use a test cross to find out the genotype of an organism showing the dominant phenotype

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78
Q

What does a test cross involve?

A

This involves crossing the unknown individual with an individual showing the recessive phenotype – if the individual is showing the recessive phenotype, then its genotype must be homozygous recessive

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79
Q

How can we tell if the individual is heterozygous or homozygous from the test cross?

A

By looking at the ratio of phenotypes in the offspring, we can tell whether the unknown individual is homozygous dominant or heterozygous

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80
Q

How can we tell from the test cross that the organism is homozygous dominant?
tall and short plants

A

If the tall plant is homozygous dominant, all offspring produced will be tall

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81
Q

How can we tell from the test cross that the organism is heterozygous?
tall and short plants

A

If the tall plant is heterozygous, half the offspring will be tall and the other half will be short

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82
Q

What are family pedigree diagrams used to show?

A

Family pedigree diagrams are usually used to trace the pattern of inheritance of a specific characteristic (usually a disease) through generations of a family

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83
Q

What can we find out by a family pedigree?

A

This can be used to work out the probability that someone in the family will inherit the genetic disorder

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84
Q

What is an example of codominance?

A

Inheritance of blood group

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85
Q

What alleles are dominant and codominant in blood groups?

A

Alleles IA and IB are codominant, but both are dominant to IO

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86
Q

What does the letter I represent in blood group alleles?

A

I represents the gene and the superscript A, B and O represent the alleles

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87
Q

What does IA produce in the blood?

A

IA results in the production of antigen A in the blood

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88
Q

What does IB produce in the blood?

A

IB results in the production of antigen B in the blood

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89
Q

What does IO produce in the blood?

A

IO results in no antigens being produced in the blood

90
Q

What does it mean if a characteristic is sex-linked?

A

When alleles that control a particular characteristic are found on the sex chromosomes, we describe the inheritance that results as ‘sex linked’

91
Q

On which chromosome are the alleles usually on and why?

A

In almost all cases, there are only alleles on the X chromosome as the Y chromosome is much smaller

92
Q

Why are males more likely to inherit sex-linked conditions?

A

Because males only have one X chromosome, they are much more likely to show sex-linked recessive conditions (such as red-green colour blindness and haemophilia)

93
Q

Why are females less likely to inherit sex-linked conditions?

A

Females, having two copies of the X chromosome, are likely to inherit one dominant allele that masks the effect of the recessive allele

94
Q

What is a woman known as if she has one recessive allele?

A

A female with one recessive allele masked in this way is known as a carrier; she doesn’t have the disease,

95
Q

What is the chance that a female carriers offspring will have a sex-linked condition?

A

she has a 50% chance of passing it on to her offspring

If that offspring is a male, he will have the disease

96
Q

What would be the result of a male who is colourblind a female carrier crossing?

A

In the cross above, there is a 25% chance of producing a male who is colourblind, a 25% chance of producing a female carrier, a 25% chance of producing a normal female and a 25% chance of producing a normal male

97
Q

What are proteins made by?

A

Proteins are made by ribosomes

98
Q

What forms proteins and what are they controlled by?

A

the sequence of amino acids controlled by the sequence of bases contained within DNA

99
Q

Can DNA travel outside the nucleus? Why?

A

DNA cannot travel out of the nucleus to the ribosomes (it is far too big to pass through a nuclear pore)

100
Q

How is the base code copied from the nucleus if it can’t leave the nucleus?

A

the base code of each gene is transcribed onto an RNA molecule called messenger RNA (mRNA).

101
Q

What happens once the base code has been transcribed to mRNA?

A

mRNA then moves out of the nucleus and attaches to a ribosome

102
Q

What does the ribosome do once it receives the mRNA?

A

The ribosome ‘reads’ the code on the mRNA in groups of three

103
Q

What does each triplet of bases do?

A

Each triplet of bases codes for a specific amino acid

104
Q

What does the ribosome do with the sequence of bases?

A

In this way the ribosome translates the sequence of bases into a sequence of amino acids that make up a protein

105
Q

What happens once the amino acid has been assembled?

A

Once the amino acid chain has been assembled, it is released from the ribosome so it can fold and form the final structure of the protein

106
Q

What does DNA control and how?

A

DNA controls cell function by controlling the production of proteins

107
Q

What are examples of proteins?

A

The proteins may be enzymes, antibodies, or receptors for neurotransmitters

108
Q

Why are some genes in certain cells not expressed?

A

Although all body cells in an organism contain the same genes, many genes in a particular cell are not expressed because the cell only makes the specific proteins it needs

109
Q

Define Inheritance

A

Transmission of genetic information from generation to generation

110
Q

Define Chromosome

A

A thread like structure of DNA carrying genetic information in the form of genes

111
Q

Define gene

A

Length of DNA that codes for a protein

112
Q

Define Allele

A

Version of a gene

113
Q

Which chromosomes do women have

A

XX

114
Q

Which chromosomes do men have?

A

XY

115
Q

Who determines the sex of the child?

A

The man

116
Q

What is the sequence of bases in a gene responsible for?

A

It is the genetic code for putting together amino acids in the correct order to make a specific protein.

117
Q

Give the base pairings

A

Thymine with Adenine

Guanine with Cytosine

118
Q

What does the DNA control?

A

Controls cell functions by controlling the production of proteins, antibodies and receptors for neurotransmitters.

119
Q

How is a protein made?

A

The DNA gene coding for the protein remains in the nucleus as it is too big
mRNA molecules carry a copy of the gene to the cytoplasm
The mRNA passes through the ribosomes
The ribosome assembles amino acids into protein molecules
The specific order of amino acids is determined by the sequence of bases in the mRNA.

120
Q

What is mRNA?

A

Messenger RNA

121
Q

How does the ribosome read the codes on the mRNA?

A

In groups of three and each triplet of bases is called a codon.

122
Q

What does a codon do?

A

Codes for a specific amino acid

123
Q

Describe the genes in body cells?

A

All body cells in an organism contain the same genes but many genes in a particular cell are not expressed because the cell only makes the specific protein it needs

124
Q

Define Haploid Nucleus

A

A nucleus containing a single set of unpaired chromosomes eg. sperm

125
Q

How many pairs of chromosomes are there in a diploid nucleus?

A

23 pairs

126
Q

Define Diploid Nucleus

A

A nucleus containing two sets of chromosomes eg. body cells

127
Q

Define Mitosis

A

Nuclear division giving rise to genetically identical cells

128
Q

What is mitosis used for?

A

It is used in growth, repair of damaged tissues, replacement of cells and asexual reproduction

129
Q

What happens in mitosis?

A

Just before mitosis, each chromosome in the nucleus copies itself exactly. Chromosomes line up along the centre of the cell where the cell fibers pull them apart. The cell divides into two and each new cell has a copy of each of the chromosomes

130
Q

What are stem cells?

A

Unspecialised cells that divide by mitosis to produce daughter cells that can be specialised for specific functions

131
Q

Define meiosis

A

A reduction division in which the chromosome number in halved from diploid to haploid resulting in genetically different cells

132
Q

When does meiosis happen?

A

It is used for the production of gametes

133
Q

What does meiosis produce?

A

Variation by forming new combinations of maternal and paternal chromosomes

134
Q

Describe the difference between mitosis and meiosis

A

Mitosis produces two cells; Meiosis produces four
Daughter cells are diploid; daughter cells are haploid
Daughter cells are genetically identical to each other; Daughter cells are genetically different to one another
One cell division occurs; Two cell divisions occur

135
Q

Define genotype

A

The genetic make-up of an organism in terms of the alleles present

136
Q

Define phenotype

A

The observable features of an organism

137
Q

Define Homozygous

A

Having the identical alleles of a particular gene

138
Q

What happens when two homozygous individuals breed?

A

Will produce pure- breeding offspring

139
Q

Define Heterozygous

A

Having two different alleles of a particular gene

140
Q

What happens when two heterozygous breed?

A

They will not produce pure breeding offspring

141
Q

Define dominant

A

An allele that is expressed if it present

142
Q

Define recessive

A

An allele that is only expressed when there is no dominant allele for the gene present

143
Q

What do breeders use test cross for?

A

To find out the genotype of an organism showing the dominant phenotype

144
Q

Give an example of codominance

A

Inheritance of blood group

145
Q

Which alleles for blood group are codominant?

A

IA and IB are both codominant to IO

146
Q

What does IA produce?

A

Antigen A in the blood

147
Q

What does IB produce?

A

Antigen B in the blood

148
Q

What does IO produce?

A

No antigens

149
Q

Which alleles give blood type A?

A

IAIA or IAIO

150
Q

Which alleles give blood type AB?

A

IA and IB

151
Q

Which alleles give blood type B?

A

IBIB or IBIO

152
Q

Which alleles give blood type O?

A

IO and IO

153
Q

Define sex-linked characteristics

A

A characteristic in which the gene responsible is located on a sex chromosome and that this makes it more common in one sex than in the other

154
Q

Which chromosomes can have alleles?

A

X chromosome

155
Q

Why are men more likely to have sex linked disease?

A

Because they only need 1 X chromosome

156
Q

What will a female with a recessive allele be?

A

A carrier

157
Q

What is an allele

A

An allele is a different form/version of the same gene (e.g. Different base sequence in the DNA)

158
Q

There are two strands coiled to form the double helix DNA. One is for dosing what is the other one for?

A

Protection

159
Q

Where are chromosomes found?

A

In the nucleus of a cell

160
Q

Where are genes located

A

On chromosomes

161
Q

What is a gene

A

A section of a molecule of DNA. It codes for a specific protein,

162
Q

What is a mutation

A

A change in the sequence of bases in DNA, it causes different forms of a gene (allele)

163
Q

What does mitosis produce

A

Identical cells. Some organisms use it for asexual reproduction

164
Q

What does meiosis produce

A

Gametes which are haploid for sexual reproduction

165
Q

How many chromosomes are there in a nuclei of a body cell

A

46

166
Q

What combination of x and y do you have if you’re a girl

A

XX

167
Q

What combination of x and y do you have if you’re a boy

A

XY

168
Q

Dominant definition

A

Only one allele needs to be like this for the characteristic to appear

169
Q

Recessive definition

A

Both alleles need to be recessive for the characteristic to appear

170
Q

Homozygous definition

A

When the two alleles in a pair are the same

171
Q

Heterozygous definition

A

When the two alleles in a pair are different

172
Q

Phenotype definition

A

The physical characteristic of an organism

173
Q

Genotype definition

A

The collection of genes inside the nucleus

174
Q

Codominance definition

A

When the phenotype is affected by both alleles working in combination

175
Q

What does mitosis help with

A

Growth, repair, cloning and asexual reproduction

176
Q

How does meiosis produce gametes?

A

It begins with a single cell (diploid) which makes a copy of each chromosome. The cell then divides into two (haploid) then each cells divides into 2 again so you have 4 haploid cells that are all genetically different.

177
Q

Inheritance

A

the transmission of genetic information from generation to generation

178
Q

Chromosomes

A

thread like structure in DNA carrying genetic information in the form of genes

179
Q

Gene

A

a length of DNA that codes for a protein

180
Q

Allele-

A

version of a gene

181
Q

Haploid nucleus

A

a nucleus containing a single set of unpaired chromosomes

182
Q

Diploid nucleus

A

nucleus containing two sets of chromosomes

183
Q

Mitosis

A

the nuclear division giving rise to genetically identical cell

184
Q

Meiosis

A

reduction division in which the chromosome number is halved from the diploid to haploid resulting in genetically different cell

185
Q

Genotype

A

the genetic make- up of an organism in terms of alleles present

186
Q

Phenotype

A

the observable features of an organism

187
Q

Homozygous

A

having two identical allele of a particular gene

188
Q

Heterozygous

A

having two different alleels of a particular gene

189
Q

Dominant

A

an allele that is expressed if it is present

190
Q

Recessive allele

A

an allele that is only expressed when there is no dominant allele of the gene present

191
Q

Sex-linked characteristics

A

characteristics in which a gene responsible Is located on a sex chromosome and that this makes it more common in one sex than in the other

192
Q

Chromosomes

A

made of DNA, which contains genetic information in the form of
genes.

193
Q

A gene is a

A

a length of DNA that codes for a protein.

194
Q

An allele is an

A

alternative form of a gene.

195
Q

female chromosomes

A

XX

196
Q

male chromosomes

A

XY

197
Q

The sequence of bases in a gene determines the

A

sequence of amino acids used to make a specific protein.

198
Q

Different sequences of amino acids give

A

different shapes to protein molecules.

199
Q

DNA controls cell function by

A

controlling the production of proteins, including
enzymes, membrane carriers and receptors for neurotransmitters

200
Q

How protein is made:

A

the gene coding for the protein remains in the nucleus
messenger RNA (mRNA) is a copy of a gene
mRNA molecules are made in the nucleus and move to the cytoplasm
the mRNA passes through ribosomes
the ribosome assembles amino acids into protein molecules
the specific sequence of amino acids is determined by the sequence of bases in
the mRNA

201
Q

Most body cells in an organism contain the same genes, but many genes in a
particular cell are not

A

expressed because the cell only makes the specific proteins it
needs. For instance, the cells in salivary gland don’t need to make protease but they
have the gene for it which is not expressed because the cell doesn’t need it.

202
Q

A haploid nucleus

A

is a nucleus containing a single set of chromosomes

203
Q

A diploid nucleus

A

is a nucleus containing two sets of chromosomes

204
Q

In a diploid cell,

A

there is a pair of each type of chromosome and in a human diploid
cell there are 23 pairs.

205
Q

Mitosis

A

nuclear division giving rise to genetically identical cells

206
Q

Role of mitosis

A

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

207
Q

Process of mitosis

A

The exact replication of chromosomes occurs before mitosis.
During mitosis, the copies of chromosomes separate, maintaining the chromosome
number in each daughter cell.

208
Q

Stem cells is unspecialised cells that divide

A

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

209
Q

Meiosis is involved in the

A

production of gametes

210
Q

Meiosis

A

reduction division in which the chromosome number is halved from
diploid to haploid resulting in genetically different cells

211
Q

Inheritance

A

transmission of genetic information from generation to generation

212
Q

Genotype

A

the genetic make-up of an organism.

213
Q

Phenotype

A

the observable features of an organism.

214
Q

Homozygous

A

having two identical alleles of a particular gene

215
Q

Two identical homozygous individuals that

A

breed together will be pure-breeding.

216
Q

Heterozygous

A

having two different alleles of a particular gene.

217
Q

A heterozygous individuals will not be

A

pure-breeding.

218
Q

dominant allele

A

is an allele that is expressed if it is present in the genotype

219
Q

recessive allele

A

an allele that is only expressed when there is no dominant allele
of the gene present in the genotype.

220
Q

Codominance

A

a situation in which both alleles in heterozygous organisms
contribute to the phenotype

221
Q

A sex-linked characteristic

A

a feature in which the gene responsible is located on a
sex chromosome and that this makes the characteristic more common in one
sex(usually male) than in the other.

222
Q

example of sex linkage.

A

Red-green colour blindness

Biology Flashcards (20 decks)

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