1
Q
What is a genome
A
The entire DNA of an organism
2
Q
What is a gene
A
A section of DNA that codes for a specific protein
3
Q
What does the nucleus of a cell contain
A
Chromosomes on which genes are located
4
Q
What is the structure of a DNA molecule
A
DNA is made up of two strands coiled together to form a double helix
5
Q
How are strands of DNA linked
A
By a series of bases
-Adenine with Thymine
-Cytosine with Guanine
Hydrogen bonds form in between the bases
6
Q
What forms the sides of the DNA ladder
A
A sugar phosphate backbone
7
Q
What is a sugar phosphate backbone made up of
A
Phosphate and deoxyribose (a sugar)
8
Q
What is a nucleotide made up of
A
Phosphate, deoxyribose and a base
9
Q
How many amino acids are there
A
20
10
Q
What is a protein
A
A protein (polymer) is a chain of amino acids (monomer)
11
Q
How does DNA control protein synthesis
A
-each gene contains a different sequence of bases, this is the genetic code
-a sequence of three bases is called a triplet
-each triplet is code for one amino acid
-amino acids join together to form proteins
-the sequence of amino acids determines the shape of a protein which determines the function
12
Q
What is RNA
A
A molecule of nucleic acid which is single stranded and contains uracil as a base instead of thymine
13
Q
Compare DNA AND RNA
A
-DNA: double stranded, thymine, triplets, longer
-RNA: single stranded, uracil, codons and anticodons, shorter
14
Q
What is transcription
A
- The double helix unwinds and the two strands seperate. This is done by an enzyme called helipads
- Complementary mRNA bases line up to the template strand of DNA- thymine pairs with adenine, adenine pairs with uracil, guanine pairs with cytosine, cytosine pairs with guanine
- RNApolymerase joins the adjacent mRNA nucleotides to form a single stranded of mRNA
- The mRNA leaves the nucleus and enters the cytoplasm
15
Q
What is translation
A
- mRNA enters the ribosomes
- The first tRNA to bind to the mRNA does so at the start codon has a specific base sequence which complements the specific amino acid that the tRNA brings
- Another tRNA brings another amino acid and the anticodon of this binds to the next codon on the mRNA
- A bond forms between the first and second amino acid
- The first tRNA molecule is released and goes off to collect another amino acid
- More tRNA molecules arrive at the mRNA and add their amino acids to the growing chain forming a protein
- At the end of the chain a stop codon tell the tRNA that the protein is complete and it is released
16
Q
What is an allele
A
Genes which exist in alternative forms which give rise to differences in inherited characteristics
17
Q
Define dominant
A
Allele of a gene that is always expressed in the hetrozygote
18
Q
Define recessive
A
Allele of a gene that is not expressed unless the dominant gene of the allele is not present
19
Q
Define homozygous
A
A genotype with the same alleles of a gene
20
Q
What is heterozygous
A
A genotype with different alleles of a gene
21
Q
Define phenotype
A
How a gene is expressed. The appearance of an organism resulting from its genotype
22
Q
Define genotype
A
Alleles an organism has for a certain characteristic
23
Q
Define codominance
A
If two alleles are expressed in the same phenotype the alleles are codminant
24
Q
What are phenotypic features a result of
A
Polygenetic inheritance rather than single genes
25
How do you draw a gene inheritance diagram
1. Identify the gene and which allele is dominant and recessive
2. Choose a letter to represent the alleles. A capital for dominant and lower case for recessive
3. Work out the phenotypes and genotypes of the parents
4.Write the genotypes of the gamete
5. Using a punnet square work out the ratios of phenotypes
26
How is the sex of a person controlled
By one pair of chromosomes, XX in a female and XY in a man
27
How is the sex of an offspring determined at fertilisation
Depends on whether the X chromosome from the girl combines with the X chromosome from the man producing a girl. Or whether the X chromosome from the girl combines with the Y chromosome from the man producing a boy
28
How many chromosomes do the human body contain
46
29
Define a diploid cell
-a cell that has 2 copies of each chromosome
-chromosomes are arranged in pairs
30
Define a haploid cell
-a cell that has one copy of each chromosome
31
Why do body cells divide by mitosis
-to make new cells to replace damaged ones
-to grow
-asexual reproduction
-cloning
32
What happens during asexual reproduction
-involved only one cell
-no gametes
-no genetic variation
-cells in one part of the body divide by mitosis
-a structure is formed which breaks away from the parent cell and grows into a new organism
-or the single celled organism divides
33
What does asexual reproduction result in
-rapid increase in numbers
-all offspring are genetically identical
34
What are the stages of mitosis
1. All chromosomes are seen as X
2. The chromosomes line up on the equator in the middle of the cell. Spindle fibres are seen that attach to the centromere in the centre of each X g
3. The chromosomes are pulled apart to each pole and the spindle fibres contract like mini muscles
4. The chromosomes unravel at the poles. New membrane form around the two sets of chromosomes to make 2 nuclei. The cytoplasm pinches together to make 2 genetically identical cells
35
What is the product of mitosis
To genetically identical diploid cells
36
Where does meiosis happen
In the male and female reproductive organs as the cell divides to form gametes
37
What are the stages of meiosis
1. One cell with a diploid number of four starts the process
2. The cell then divides into four cells which contain one set of chromosomes. These are haploid cells
3. The cells made are genetically varied and are gametes
38
What is random fertilisation
-it is pure chance which of the millions of sperm which are released will fertilise the egg
-it is also random which egg is released during ovulation
-the random fertilisation gives variation and explains why siblings are different
39
What is the diploid number of chromosomes in human cells
46
40
What is the haploid number of chromosomes in human cells
23
41
What is polygenic inheritance
Inheritance that is controlled by many genes and usually shows continuous variation
42
What are the causes of variation within a species
-Genetic (genes inherited)
-Environmental (conditions in which they are developed)
-A combination of both
43
What are two examples of genetic variation
-blood group
-natural hair colour
44
What are two example of environmental variation
-Scars
-Spoken language
45
What are two example of both genetic and environmental variation
-intelligence
-body mass
46
What is a mutation
A random and rare change to the DNA base sequence
47
How can a change in DNA from a mutation affect the phenotype
-For protein synthesis to occur, the DNA sequence needs to be transcribed and translated
-Hence when mutations change the base sequence of DNA this will the change the base sequence of the complementary mRNA made during transcription
-As a result, a modified mRNA will be translated and will code for different sequenced of amino acids in the chain that forms the protein
-Consequently, the shape of the protein is altered
-If the protein shape is altered, then it may not be able to carry out its normal function in the cells, giving the cells a different characteristic/ phenotype
-An organism whose cells have different characteristics will have a different function
48
Hoe often do genetic mutations effect the phenotype
Usually most genetic mutations have no effect on the phenotype, some have a small effect and rarely do they have a significant effect
49
What are the harmful effects of mutations
-Can alter base sequence of DNA and destroy protein's normal function
-Can cause genetic disorders that can be passed down to future generations
-can cause an obvious effect on the phenotype of an individual
50
What are the neutral effects of mutations
-Can alter the base sequence in DNA but have no effect on the function of a protein
-May not affect the chances of survival of an individual
51
What are the beneficial effects of mutations
-Can alter the base sequence in DNA so the DNA codes for a different protein, allowing the organism to be better adapted to its environment, increasing the chances of survival
-May be passed onto generations increasing survival chances for the whole species
-can be found in all organisms such as carriers of the sickle cell allele are more resistant to malaria
52
What happens during a substitution mutation
Only one codon in the base sequence is changed
53
What happens during an insertion mutation
causes a frame shift so all codons after the extra base are changed
54
what happens during a deletion mutation
also causes a frame shift after the deleted codon
55
How can the incidence of mutations be increased
-Exposure to ionising radiation eg uv light, x-rays and gamma rays
-Chemical mutagens such as tar from cigarette smoke
56
How do you get full marks on a question on evolution
1. There is natural variation in all population
2. A chance mutation produces a new allele
3. This new allele gives the organism a selective advantage which can be useful if the environment is changing
4. Those better suited to the environment will survive and reproduce and those individuals less suited will die
5. The beneficial allele will be passed on
6. The number of individuals with the characteristic will increase in the population
7. Overtime (millions of years) the species will evolve
57
What is Darwin's theory of evolution by natural selection
Populations will slowly change or evolve as successful parents pass on alleles to their offspring
58
What is antibiotic resistance
If a bacteria cannot be killed by a certain antibiotic then we say that it is resistant to that type of antibiotic
59
Why is it important that you have the correct antibiotic for the bacteria
If an antibiotic is not specific to a bacteria it will not kill it and it will survive and reproduce whilst passing on the beneficial allele. Overtime this can create a superbug which can be resistant to many different types of antibiotics
Biology
flashcards
Decks in class (16)
# Cards
-
Reproduction In Humans47
-
Transport In Humans77
-
Ecology51
-
Human Influences On The Environment30
-
Reproduction In Flowering Plants38
-
Coordination And Response In Humans68
-
Coordination And Response In Plants10
-
Enzymes and human nutrition70
-
Excretion19
-
Plant Nutrition41
-
Transport In Plants29
-
Genetics, Inheritance And Evolution59
-
Gas exchange and breathing33
-
Movement into and out of cells10
-
Gene Technology39
-
Food Production41
