Inheritance, evolution etc. Flashcards
1
Q
How many pairs of chromosomes do human cells contain?
A
23 pairs
2
Q
Give one way cells can divide
A
Mitosis
3
Q
Name one type of cell where the chromosomes are not paired?
A
Gametes(sperm and egg cells in humans)
4
Q
How many single chromosomes are there in a gamete?
A
23
5
Q
When meiosis takes place in plants, what are the gametes?
A
Pollen and egg cell
6
Q
What does sexual reproduction involve?
A
The fusion of male and female gametes
7
Q
What is fertilisation
A
The process where male and female gametes are fused
8
Q
What does sexual reproduction involve?
A
the mixing of genetic information
9
Q
How do aphids reproduce?
A
Asexual reproduction
10
Q
How many parents in asexual reproduction?
A
1
11
Q
Does asexual reproduction involve gametes?
A
No
12
Q
What are gametes?
A
An organisms reproductive cell
13
Q
What do we call the offspring produced(asexual)
A
Clone
14
Q
What does asexual reproduction involve?
A
Mitosis
15
Q
Explain how a plant reproduces asexually
A
Tiny buds are formed by plant then they fall off and grow into new offspring they are genetically identical to the parent
16
Q
Where does meiosis take place?
A
Reproductive organs(testes in males and ovaries in females)
17
Q
Describe the process of meiosis in humans
A
A cell is in the reproductive organs of a human
.the chromosomes are copied
.Cell then divides into two
.Now both of these cells divide into two one more time forming gametes(chromosomes are no longer in pairs)
18
Q
How many gametes are produced from one original cell?
A
4
19
Q
Do all gametes have the same alleles?
A
No, they all have different alleles and different genetic information
20
Q
What happens to the gametes produced from meiosis
A
They fuse together in sexual reproduction
21
Q
After fertilisation how many chromosomes does the cell have
A
46(23 pairs)
22
Q
What happens after meiosis and fertilisation?
A
Cell divides by mitosis producing a clump of identical cells known as an embryo
23
Q
What happens to the cells in embryo over time
A
They differentiate to different cell types
24
Q
What do cells in an embryo in an animal differentiate to?
A
Muscle and nerve cells
25
In sexual reproduction the offspring have genetic information from two parents hence the offspring has genetic variation give an advantage to this
If there is a change in the environment then some of the offspring may be able to survive so sexual reproduction gives survival advantage via natural selection
26
Elaborate on the advantage of sexual reproduction
Gives a species a greater chance of survival if conditions become challenging(have to know this)
27
Name another advantage of sexual reproduction for humans
We can selectively breed a modern strain of wheat to give a high yield of good quality grain
28
Name an advantage of asexual reproduction?
only one parent involved so no need to find a mate more efficient in time and energy
29
Name another advnatage?
because its fast, asexual reproduction is extremely useful when conditions are desirable as many offspring can be produced rapidly
30
Give on disadvnatage
Very risky because all offspring can die if conditions become unfavourable as they all have same genetic information
31
Explain when malaria parasite produce sexually and asexually
The malaria parasite has part of its life in a human host and in a mosquito vector, it reproduces asexually in human host and sexually in mosquito vector
32
Explain how fungi can reproduce sexually and asexually?
Many fungi reproduce asexually to this they produce spores they can also reproduce sexually
33
Explain how a strawberry plant reproduces asexually
they produce asexually by sending out runners, where the runner touches the soil it can develop into a new plant genetically identical to parent
34
How do plants reproduce
Sexually to produce seeds (some can produce asexually)
35
Explain how daffodils can reproduce asexually?
By bulb division, the parent plant has an underground bulb which produces bubs, these buds eventually form new offspring plants
36
Where are chromosomes found?
In the nucleus of cells
37
What do chromosomes contain?
The molecule DNA (the genetic material)
38
Why do scientists say that DNA is our genetic material?
This is because our DNA determines our inherited features
39
Describe the structure of DNA
DNA consists of two strands each strand is called a polymer, each strand is made up of lots of small molecules, in DNA the two strands wrap around each other forming a double helix structure
40
What is a gene?
A small section of DNA on a chromosome
41
What do genes do?
Encode for a specific sequence of amino acids to make a specific protein, the blood type gene encodes the sequence of amino acids for the protein that determines blood type
42
How many genes does chromosome 9 have?
Well over 700
43
What type of genes does chromosome 9 have?
Genes for blood type
44
What is a genome?
The entire genetic material of a organism
45
Give some benefits of scientists studying the entire human genome
It will help us search for genes linked to disease e.g., genes that increase the risk of developing cancer or Alzhoimer's disease, helps us understand and treat inherited disorders such as cystic fibrosis
46
Give another reason why understanding the human genome may be beneficial
We can use human genome to help trace migration patterns from the past, helping people discover ancestry
47
What is DNA a polymer of?
Molecules called nucleotides
48
Describe the structure of a nucleotide?
Its a phosphate group attached to a sugar molecule, the sugar molecule is then attached to a base (look at diagram)
49
Does the sugar molecule and phosphate group ever change?
NO
50
How many different bases are there?, name them
4, ACGT
51
How many different nucleotides does DNA contain
4
52
What are DNA strands?
Complementary, so the same bases always pair on the two opposite strands, C is linked to G, A is always linked to T
53
How many different amino acids are there in humans?
20
54
What determines the shape of the protein?
The specific order of amino acids
55
What does the shape of the protein determine
Its function
56
Give an example of three proteins?
Amylase, Collagen and insulin
57
What type of protein is amylase?
An enzyme molecule
58
What type of protein is Collagen?
A structural protein
59
What type of protein is insulin?
A hormone
60
What is the order of amino acids determined by?
The sequence of bases in the gene for that protein
61
How does the cell read the short stretch of DNA
The cell reads the DNA sequence as triplets of bases, each triplet encodes for a specific amino acid in the protein
62
Where do the first and second stages of protein synthesis take place?
First stage in the nucleus and second in the cytoplasm
63
What is the first stage called?
Transcription
64
Explain the first stage?
The base sequence of the gene is copied into a complementary template molecule called mRNA ( m is for messenger) mRNA now passes out of the nucleus into the cytoplasm
65
Is mRNA single stranded?
No it is single stranded
66
What is the second stage of protein synthesis called?
Traslation
67
Explain the second stage?
The mRNA molecule attaches to a ribosome, amino acids are then brought to the ribosome on carrier molecules, (known as tRNA, t is for transfer), ribosome reads the triplets of bases on the mRNA and uses this to join together the correct amino acids in the correct order once the protein chain is complete it folds into a unique shape which enables the protein to do its job e.g. enzyme
68
What is a change to a base called?
A mutation, mutations happen all the time
69
Why could the sequence of amino acid stay the same if the base is changed?
Different base triplets can sometimes code for the same amino acid
70
Do most mutations have an effect on the proteins function or shape?
No
71
Explain the possible effect on a protein(e.g. enzyme) if there is a mutation in a gene?
There will be a change in a base in the gene, causing a different amino acid in the protein, altering the shape of the protein, causing a dramatic effect on the function of the protein e.g. the active site of an enzyme may change meaning it can no longer bind to its substrate
72
What is the effect if a mutation changes the shape of a structural protein (e.g. collagen)
it may lose its strength
73
What do chromosomes also contain?
non-coding parts of DNA
74
What do non-coding parts of DNA do?
Switch genes on and off
75
Explain the effect if there is a mutation in a non-coding part of DNA
A gene may be turned on when it should be turned off, so a cell can produce a protein that its not meant to have at that time, this can have many effects e.g. uncontrolled mitosis which can lead to cancer
76
How many copies of a chromosome do human cells contain?
2 copies of each chromosmoe
77
Where does one chromosome form the pair come from and the other?
One from your father and one from your mother
78
How many copies of each gene have we got?
2 due to each chromosome having the same gene
79
How many genes code for ear wax
1
80
How many genes are most characteristics controlled by?
Many genes acting together
81
What are alleles?
Versions of genes
82
How many alleles are there in the gene for ear wax?
2 alleles
83
What does the genotype tell us?
The alleles present
84
What is a persons genotype if he contains two alleles for dry ear wax (e)
(ee)
85
What does it mean to be homozygous?
To have two copies of the same allel
86
What does the phenotype tell us?
The characteristics caused by the person's alleles
87
What is the phenotype for someone who has two alleles for dry ear wax?
Dry ear wx
88
What is the phenotype for someone who has two alleles for dry ear wax?
Dry ear wax
89
What does it mean to be hetrozygous?
To have two different alleles
90
If someone has a allele for wet and dry ear wax what will the phenotype be?
Depends which one is dominant (capital letter)
91
What is cystic fibrosis?
A inherited disorder , disorder of cell membranes
92
How many genes is cystic fibrosis controlled by?
A single gene with two alleles
93
what is needed to inherit cystic fibrosis?
The person has to have two copies of the defective cell membrane allele and no copies of the normal cell membrane function allele
94
What does it mean to be a carrier of the cystic fibrosis allele
To have one normal allele and have one defective allele
95
How do we find out whether or not or the chance that a couple may have cystic fibrosis?
By using a punnet square
96
Learn how to do punnet square
ashkdb
97
what is polydactyly caused by?
A dominant allele, so one person with one copy of the dominant allele and one copy of the recessive allele will have polydactyly
98
Can u be a carrier of a dominant allele?
No
99
If there is a 50% chance of getting polydactyly what is the ratio?
1:1
100
Give a solution to inherited disorders
Embryo screening,
101
What happens in embryo screening
Embryos are tested to see if they have the alleles for inherited disorders, embryos without the defective allele are implanted into a woman, then develop into healthy offspring
102
Give issues to embryo screening
.Its expensive, some people think that the money should be spent elsewhere in the health service
. only a small number of embryos are implanted and a large number of embryos are created so some healthy embryos are destroyed some people find this unethical
.in the future we may be able to screen offspring with desired characteristics, many people find this unethical
103
What is gene therapy?
Correcting faulty alleles and using that to treat inherited disorders, still experimental
104
What does a family tree show?
Phenotype
105
Use a family tree to prove that cystic fibrosis is recessive?
Both of the offspring's parents do not have cystic fibrosis so they must be carriers however the offspring has it meaning it has to be recessive if it was caused by a dominant allele then one of the parents would have cystic fibrosis
106
How many chromosome pairs contain the genes which determine inherited characteristics only?
22
107
What chromosomes do males and females have?
Men have XY females have XX
108
What is the chance of having a female or male baby?
50%
109
How can we prove that there is a 50% percent chance of having a male or female?
By using a punnet square putting the female chromosomes XX in the left and XY on the top you will find out that there is a 50% chance that offspring will have XY and vice versa
110
What is variation?
All the differences in characteristics of individuals in a population
111
Give a causes of variation?
Alleles which people have inherited(genetic), the environment too
112
Give examples of variation?
Hair colour and eye colour, language in humans
113
Explain how the environment can cause variation
The colour of certain flowers depends on the PH of the soil
114
Give examples of variation caused by genes and the environment
Height, some people have alleles which make them more likely to grow taller however they must also include enough calcium in their diet for their bones to fully develop
115
What is the cause for genetic variation?
Mutations, random changes to DNA
116
Give an example of how a mutation can benefit the environment?
In the 1950s a virus spread in the UK which killed over 99% of wild rabbits, a mutation occurred which made the surviving rabbits resistant to the virus
117
How many different species of animals are there in the world?
Around 9 million(1% of all the species that have ever lived on earth)
118
Give an example of natural selection by evolution in rabbits
If the environment were to get colder, rabbits who have inherited alleles for thicker fur are more likely to survive in these cold temperatures than rabbits with thin thinner fur, hence rabbits with thicker fur are more likely to go on to reproduce, their offspring could inherit the alleles for thicker fur, these offspring are also more likely to survive the cold and reproduce, over many generations the alleles for thicker fur will be widespread among the rabbit population
119
Give an example of natural selection by evolution in rabbits due to foxes
A fox moves into an area, the rabbits which have the alleles for better eyesight or better hearing are more likely to survive and go on to reproduce as they can detect foxes quicker these offspring are also more likely to survive and reproduce if a predator moves into the area the beneficial allele is then passed on and over many generations the alleles for better eyesight or hearing are widespread among the rabbit population
120
Define evolution
The change in the inherited characteristics of a population over time through a process of natural selection
121
Explain what can happen to a species as a result of evolution
Sometimes two populations of one species can become so different in phenotype that they can no longer interbreed to give fertile offspring, the population has become two different species
122
Give an example of two different species of rabbits
A pygmy rabbit they are so small that they cant breed with normal sized rabbits successfully, so they are a different species
123
Explain why wolfs are useful?
They can alert humans if a threat is approaching and can keep us company and warm,
124
Have wolfs been selectively bread to give dogs?
Yes
125
Explain 4 things humans have selectively bread
We have selectively bred domestic dogs to have a more gentle nature
.We have selectively bread food crops such was wheat to be resistant to disease
.Animals such as cows have been selectively bread to produce more milk or meat
.Certain plants have been selectively bred to produce large or unusual flowers
126
How is selective breeding carried out in cows for more meat?
We take a mixed population of cows and select the largest male and female, we then breed these together, sexual reproduction produces variation in the offspring so the offspring will be a mixture of larger and smaller animals, we select the largest male and female and breed these together, we continue to do this over many generations until all the offspring are large
127
Name some problems with selective breeding
if we breed together close related animals or plants, then we get inbreeding which can cause some breeds to be more prone to disease or inherited defects
128
Give an example of a breed which has suffered from inbreeding
Dog breeds have been selectively bred for hundreds of generations, many dog breeds developed inherited disease such as epilopsy, joint problems or heart disease
129
What happens in genetic engineering?
Genes from one organism are cut out and transferred to cells of another organism, the genome of the organism receiving the gene is modified and now includes another organisms DNA
130
Explain how genetic engineering is carried out with insulin?
Insulin is a hormone involved in blood regulation in humans, we can genetically modify bacteria to contain the human insulin gene, the bacteria then produces human insulin, this insulin can be purified and used for people with type one diabetes who cant produce their own insulin
131
Explain the benefits in genetically modified crops
GM crops usually produce a grater yield than normal crops, we can make GM crops resistant to disease or insect attack, or make them produce bigger and better fruits
132
Give an advantage to GM crops being resistant to herbicides?
Farmers can spray their crops to kill weeds without harming the GM crop
133
Give disadvantage of GM crops?
Health effects are unknown and they can be harmful to insects or to wild flowers
134
Give a disadvantage of gene therapy
Long-term effects are unknown
135
Give all the steps in genetic engineering
. First we identify the gene we want to transfer we then use enzymes to isolate this gene, now we transfer this gene to a small circle of DNA called a plasmid( we can use a virus instead of a plasmid) the plasmid transfers the desired gene into the cells of the target organism
136
Where did plasmids come from and what are they useful in?
They came from bacteria they are useful in transferring DNA from one organism to another
137
Why do we transfer the gene at an early stage of an organism's development
To make sure every cell receives the desired gene(as there are a few amount of cells) so the organism develops with the characteristic that we want
138
Why do we transfer the gene at an early stage of an organism's development
To make sure every cell receives the desired gene(as there are a few amount of cells) so the organism develops with the characteristic that we want
