Human Biology Unit 4 > Chapter 9.1 Mutations > Flashcards

Chapter 9.1 Mutations Flashcards

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1
Q

What is evolution?

A

The gradual and inheritable change of a characteristics of a species over a number of generations

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2
Q

What is phenotype?

A

The observable characteristic due to the genotype

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3
Q

What is genotype?

A

The combination of alleles for a gene

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4
Q

What is a population?

A

A group of organisms of the same species living together in a particular place at a particular time.

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5
Q

What is gene pool?

A

The sum of all the alleles in a given population

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6
Q

What is allele frequency?

A

How often each allele of a gene occurs in the gene pool of a population

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7
Q

What is a mutation?

A

A change in a gene or chromosome leading to new characteristics in an organism

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8
Q

What is a mutagenic agent?

A

An environmental that increases the rate of mutation

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9
Q

What are the two main types of mutations?

A

Gene mutation and Chromosomal mutation

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10
Q

What is a gene mutation?

A

An alteration to a single gene

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11
Q

What is a chromosomal mutation?

A

A change to the structure and/or number of chromosomes in an organism

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12
Q

When can mistakes that lead to mutations occur?

A

They can occur spontaneously during DNA replication in mitosis or meiosis, or when chromosomes are separated during meiosis.

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13
Q

What happens to many mutations that occur in cells?

A

Many mutations are repaired and therefore do not cause a problem

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14
Q

What happens if a mutation is not repaired?

A

It is copied during cell division and passed onto daughter cells

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15
Q

What is the significance if a mutation occurs in gametes?

A

It can be passed on from generation to generation

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16
Q

Why are mutations relatively rare in humans despite millions of cell divisions?

A

Because DNA replication is highly accurate and many mutations are repaired

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17
Q

How can mutations contribute to human survival?

A

Some mutations produce traits better suited to an environment, which may improve survival chances.

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18
Q

What are some examples of mutagens?

A

-Mustard gas
-Formaldehyde
-Sulfur dioxide
-Some antibiotics
-All kinds of ionising radiation e.g. UV, X-rays, cosmic rays, radiation from radioactive waste and fall out from atomic and nuclear explosions.

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19
Q

What shape is DNA composed of?

A

Double helix

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20
Q

What are the four nucleotides present in DNA?

A

Adenine, thymine, guanine and cytosine

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21
Q

What is the backbone of DNA made of?

A

Sugar-phosphate groups

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22
Q

What is used to code for amino acids used to build proteins with?

A

The sequence of the bases in DNA

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23
Q

What is Albinism?

A

An inherited inability to produce pigment in hair, skin and eyes

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24
Q

What are induced mutations?

A

A mutation causes by a mutagenic agent

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25
What are spontaneous mutations?
A mutation that occurs due to a random error in a biological process such as mitosis and meiosis
26
What are somatic mutations?
A mutation occurring in the gene of a body cells
27
In a somatic mutation, can it be passed on?
No, it only affects the cell that has the mutation and cannot be passed on
28
What are germline mutations?
A mutation occurring in a the gene of a germline cell (that arises into a gamete)
29
What is phenylketonuria?
An inherited disease resulting in the damage to the growing brain and, thus, intellectual deficiency, tendency towards epileptic seizures, and failure to produce normal skin pigmentation
30
In a germline mutation, can it be passed on?
Yes it can, it can be passed onto daughter cells
31
What are the five classified effects of the mutation?
-Missense -Nonsense -Neutral -Silent
32
What is a missense mutation?
Its a mutation that changes the amino acid in the gene and therefore changes the protein produced
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What is a nonsense mutation?
-Its a mutation that changes the base sequence to a STOP codon. -This means that the synthesis of the protein will stop and so a shorter protein is produced that is unlikely to be able to fulfil its function
34
What is a neutral mutation?
Its a mutation that causes a change in an amino acid however the amino acid codes for the same protein.
35
What is a silent mutation?
Its a mutation that does not cause any change in the amino acid and therefore in the protein produced. -This is possible, as most amino acids are coded for by more than one base sequence
36
A gene mutation affects ____ gene, while a chromosomal mutation affects ______ genes
A gene mutation affects a single gene A chromosomal mutation affects a number of genes
37
What are point mutations?
A mutation that changes a single base in the DNA sequence
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What are the three subdivisions of a point mutation?
Insertion Substitution Deletion
39
What is insertion?
A new nucleotide is added to the DNA strand
40
What is substitution?
An existing nucleotide is replaced with another one, with a different base
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What is deletion?
A nucleotide is removed from the DNA strand
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What is a frameshift mutation?
A mutation involving an insertion or a deletion that results in a change in the way that the sequence is read
43
What does frameshift mutations affect the outcome of?
Affects the outcome of all of the DNA from that point on
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What are the different types of frameshift mutation?
-Duplication -Deletion -Inversion -Translocation -Non-disjunction
45
What is duplication?
A section of chromosome occurs twice
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What is deletion (frameshift)?
A piece of DNA is removed
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What is inversion (frameshift)?
Breaks occur in a chromosome and the broken piece joins back in, but the wrong way around
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What is translocation?
Part of a chromosome breaks off and is rejoined to the wrong chromosome
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What is non-disjunction?
During meiosis, a chromosome pair does not separate and so one daughter cell has an extra chromosome and one daughter cell has one less than the normal number.
50
What is aneuplodiy?
A change in the chromosome number as a result of non-disjunction
51
What mutation causes Duchenne muscular dystrophy?
Gene mutation
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How can Duchenne muscular dystrophy be inherited?
It can result from a mutation in the mother and be inherited by her sons
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Besides inheritance, how else can Duchenne muscular dystrophy occur?
Through a spontaneous mutation in a male zygote
54
At what age do symptoms of Duchenne muscular dystrophy usually appear?
Around 3-5 years old
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What causes death in individuals with Duchenne muscular dystrophy?
Failure of the respiratory muscles
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What is Duchenne muscular dystrophy?
-A condition caused by a gene mutation that leads to the progressive wasting of muscles. -Typically seen in boys, either inherited from a carrier mother or arising from a spontaneous mutation in a male zygote
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What causes cystic fibrosis?
A gene mutation on chromosome number 7
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What does the gene affected in cystic fibrosis normally code for?
A protein that regulates the passage of chloride ions across the cell membrane
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What happens when the correct protein is not produced in a person with cystic fibrosis?
The person experiences symptoms like salty-tasting skin, persistent coughing, wheezing or pneumonia and digestive problems
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Is the mutant allele that causes cystic fibrosis dominant or recessive?
Recessive
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How does a person inherit cystic fibrosis?
They must inherit the mutant allele from both parents
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What is trisomy caused by?
Non-disjunction during the second division of meiosis
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What happens to the eggs or sperm when non-disjunction occurs?
They have either one chromosome too many or one chromosome missing
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What is Down syndrome also known as?
Trisomy 21
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What causes Down syndrome?
The presence of three copies of chromosome 21 instead of two
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In which group is Down syndrome more likely to occur?
Children of older mothers
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What are some characteristics of a person with Down syndrome?
Characteristic facial expression Intellectual disability Weak muscles
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What birth defects are commonly associated with Down syndrome?
Heart defects and digestive abnormalities
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What is partial trisomy?
It occurs when part of an extra chromosome 21 is attached to another chromosome
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What syndrome is caused by trisomy of chromosome 13
Patau syndrome
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What are the features of Patau syndrome?
Intellectual disability Microcephaly Extra fingers Cleft palate and/or lip Malformations of the ears and eyes
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Where can the extra chromosome 12 in Patau syndrome come from?
Either the mother's egg or the father's sperm
73
What happens in sex chromosome trisomy in males?
Non-disjunction results in an extra X (XXY) or Y (XYY) chromosome
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What conditions do male with an XXY trisomy develop as adults?
Klinefelter syndrome
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What are the characteristics of Klinefelter syndrome?
Small testes with no sperm production Enlarged breasts Sparse body hair Sometimes intellectual disability
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What is monosomy?
A condition where an individual is missing a chromosome?
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What is partial monosomy?
A condition where only part of a chromosome is missing
78
What is cri-du-chat syndrome?
A rare genetic disorder caused by a missing portion of chromosome 5, resulting in characteristic car-like cry in infants
79
What causes the characteristic cry in cri-du-chat syndrome?
Problems with the larynx and nervous system
80
What is monosomy X and what syndrome does it cause?
Monosomy X is when a female has only one X chromosome, causing Turner syndrome
81
What are the characteristics of Turner syndrome?
Short Stature Lack of secondary sexual characteristics Infertility
82
Why are most gene mutations recessive?
Because they prevent the gene from producing a functioning protein, but the normal dominant allele masks the effect
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What is a lethal recessive?
A recessive mutation that causes death when not masked by a normal dominant allele
84
How do lethal recessives affect the gene pool?
They reduce the number of lethal alleles in the population because affected individuals die before passing them on
85
What is Tay-Sachs disease (TSD)?
A lethal recessive disorder of lipid metabolism caused by a mutation in the HEX gene
86
What enzyme is missing in Tay-Sachs disease?
beta-hexosaminidase
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What substances accumulates in the nervous system in Tay-Sachs disease?
GM2 ganglioside
88
What happens to a child with Tay-Sachs disease?
They develop normally for a few months, the progressively deteriorate intellectually and physically, usually dying in early childhood
89
Explain why only germline mutations are passed onto the next generation?
-Only germline mutations occur in the gametes (sperm or egg cells), which are involved in reproduction. When a gamete carrying a mutation is used in fertilisation, the mutation becomes part of the zygote's DNA and will be present in every cell of the resulting offspring.
90
List two conditions due to: a) Gene mutations b) Chromosomal mutations
a) Tay-Sachs disease Duchenne Muscular dystrophy b) Down Syndrome (Trisomy 21) Cri-du-chat syndrome (partial monosomy of chromosome 5)
91
Is Down syndrome an example of gene mutation or a chromosomal mutation? Explain your answer
-Chromosomal because it is caused by trisomy 21, where there are three copies of chromosome 21 in
92
Use Tay-Sachs disease as an example to explain how a gene mutation can be lethal
Human Biology Unit 4
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