B1 - You and Your Genes Flashcards
State the two types of cell
State the two types of cell
Eukaryotic (animals and plants) and
prokaryotic
What is the difference between a
eukaryotic and prokaryotic cell?
What is the difference between a eukaryotic and
prokaryotic cell?
A eukaryotic cell contains a nucleus and
membrane-bound organelles. A
prokaryotic cell does not.
How can the structure of eukaryotic cells
be observed?
How can the structure of eukaryotic cells be
observed?
Using a light microscope
How is genetic information stored in a
eukaryotic cell?
How is genetic information stored in a eukaryotic
cell?
Within the nucleus, arranged in
chromosomes
How is genetic information stored in a
prokaryotic cell?
How is genetic information stored in a prokaryotic cell? Found free within the cytoplasm as: ● Single large loop of circular DNA ● Plasmids
What are plasmids?
What are plasmids?
● Small, circular loops of DNA found free in the
cytoplasm and separate from the main DNA
● Carry genes that provide genetic advantages
e.g. antibiotic resistance
Define genome
Define genome
The entire genetic material of an organism
What is a chromosome?
What is a chromosome?
A long, coiled molecule of DNA that carries genetic information in the form of genes
What is DNA?
What is DNA?
A double-stranded polymer of nucleotides, wound to form a double helix
Define gene
Define gene
A section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein
What are alleles?
What are alleles?
Different versions of the same gene
Define genotype
Define genotype
An organism’s genetic composition, describes all alleles
Define phenotype
Define phenotype
An organism’s observable characteristics due to interactions of the genotype and environment (which can modify the phenotype)
What are the monomers of DNA?
What are the monomers of DNA?
Nucleotides
What are DNA nucleotides made up of?
What are DNA nucleotides made up of?
● Common sugar
● Phosphate group
● One of four bases: A, T, C or G
Describe how nucleotides interact to
form a molecule of DNA
Describe how nucleotides interact to form a molecule
of DNA
● Sugar and phosphate molecules join to form a
sugar-phosphate backbone in each DNA strand
● Base connected to each sugar
● Complementary base pairing: A pairs with T, C pairs with G
Explain how a gene codes for a protein
Explain how a gene codes for a protein
● A sequence of three bases in a gene forms a triplet
● Each triplet codes for an amino acid
● The order of amino acids determines the structure
and function of protein formed
Describe the differences between mRNA
and DNA
Describe the difference between mRNA and DNA
● mRNA is single stranded whereas
DNA is double stranded
● mRNA uses U whereas DNA uses T
What is protein synthesis?
What is protein synthesis?
The formation of a protein from a gene
Outline protein synthesis
Outline protein synthesis
1. In the nucleus, DNA is used as a template to form mRNA
2. mRNA exits the nucleus, moving into the cytoplasm where
it attaches to a ribosome
3. The ribosome joins amino acids in a specific order,
dictated by mRNA to form a protein.
Why does mRNA rather than DNA join to
a ribosome in the cytoplasm
Why does mRNA rather than DNA join to a ribosome
in the cytoplasm?
DNA is too large to leave the nucleus so cannot reach the ribosome
What is a mutation?
What is a mutation?
A random change to the base sequence
of DNA which results in genetic variants
State the three types of gene mutation
State the three types of gene mutation
● Insertion
● Deletion
● Substitution
Describe the effect of a gene mutation in
coding DNA
Describe the effect of a gene mutation in coding
DNA
● If a mutation changes the sequence of amino acids,
protein structure and function may change
● If a mutation does not change the sequence of amino acids, there is no effect on protein structure or
function
What is non-coding DNA?
What is non-coding DNA?
DNA which does not code for a protein
but instead controls gene expression
Describe the effect of a gene mutation in
non-coding DNA
Describe the effect of a gene mutation in non-coding
DNA
Gene expression may be altered, affecting protein production and the resulting phenotype
What are gametes?
What are gametes? Reproductive cells (e.g. egg and sperm cells) that contain a single copy of each chromosome
Describe sexual reproduction in terms of
chromosome number
Describe sexual reproduction in terms of
chromosome number
● Two gametes with a single copy of each
chromosome fuse
● Resulting embryo has two chromosomes for
each gene and two copies of each allele
Define homozygous
Define homozygous
Having two identical alleles of a gene
e.g. FF or ff
Define heterozygous
Define heterozygous
Having two different alleles of a gene
e.g. Ff
What is a dominant allele?
What is a dominant allele?
Describes an allele that is always expressed
Represented with a capital letter e.g. F
What is a recessive allele?
What is a recessive allele?
An allele that is only expressed in the absence of a dominant allele
Represented with a small letter e.g. f
A female who is homozygous recessive for cystic fibrosis (ff) has a child with a heterozygous male (Ff). Draw a punnett square to illustrate this single gene inheritance.
check
What is the problem with single gene
crosses?
What is the problem with single gene crosses?
Most characteristics are controlled by multiple alleles rather than just one
What are sex chromosomes?
What are sex chromosomes?
A pair of chromosomes that determines sex:
● Males have an X and a Y chromosome
● Females have two X chromosomes
Why does the inheritance of a Y
chromosome mean that an embryo
develops into a male?
Why does the inheritance of a Y chromosome mean
that an embryo develops into a male?
Testes development in an embryo is stimulated by a gene present on the Y chromosome
Check CGP for punnet squares
yessir
Other than using a punnett square, how
else can single gene inheritance be
represented?
Other than using a punnett square, how else can
single gene inheritance be represented?
Using a family tree
Outline how the work of Mendel helped
scientists to develop their understanding
of genetics
Outline how the work of Mendel helped scientists to
develop their understanding of genetics
● Mendel studied the inheritance of different phenotypes of pea plants
● He established a correlation between parent and offspring phenotypes
● He noted that inheritance was determined by ‘units’ passed on to
descendants
● Using gene crosses, he devised the terms ‘dominant’ and ‘recessive’
What is genome sequencing?
What is genome sequencing?
Finding out the order of nucleotides in the DNA of an organism, enabling the function and interaction of genes to be assessed
Why is genome sequencing important?
Why is genome sequencing important?
● Allows the comparison of genomes of healthy
individuals with patients who have a disease
● Potential disease-causing alleles are identified
● Individuals can then undergo genetic testing for these alleles
Outline how genetic testing can be used
to improve healthcare (3)
Outline how genetic testing can be used to improve
healthcare (3)
● Enables awareness of potential risks and the introduction
of lifestyle changes to reduce these associated risks
● Enables early treatment plans to begin
● Prediction of a patient’s reaction to certain drugs -
‘personalised medicine’
Outline the drawbacks of using genetic
testing in healthcare (2)
Outline the drawbacks of using genetic testing in
healthcare (2)
● Discrimination by employers, insurance firms
etc. if a person is likely to develop a disease
● Person may develop anxiety, depression etc.
Outline how genetic testing can be used
in family planning (3)
Outline how genetic testing can be used in family
planning (3)
● Parental carrier testing - parents tested for the presence of recessive disease-causing alleles
● Prenatal testing - egg fertilised In vitro, embryo tested for genetic disorders
● Fetus tested for genetic disorders via amniocentesis or chorionic villus sampling (CVS)
Outline the drawbacks of using genetic
testing in family planning (4)
Outline the drawbacks of using genetic testing in
family planning (4)
● False-positive/false-negatives
● Ethical considerations - involves the destruction of
embryos and potential terminations
● Amniocentesis and CVS carry a slight risk of miscarriage
● Could lead to ‘designer babies’
What is genetic engineering?
What is genetic engineering?
● The changing of the genome of an organism by the
insertion of a desired gene from another organism
● Enables the formation of an organism with beneficial
characteristics
Describe the process of genetic
engineering
Describe the process of genetic engineering
- Desired gene isolated using enzymes
- Gene replicated
- Gene placed into vector (e.g. plasmid, virus)
- Vector mixed with and ‘taken up’ by target cells
- Modified cells identified, selected and cultured
Describe the benefits of genetic
engineering (3)
Describe the benefits of genetic engineering (3)
● Increased crop yields for growing population e.g.
herbicide-resistance, disease-resistance
● Useful in medicine e.g. insulin-producing bacteria, antithrombin in goat milk
● GM crops produce scarce resources e.g. GM golden rice produces beta-carotene (source of vitamin A in the body)
Describe the risks of genetic engineering
Describe the risks of genetic engineering (3)
● Long-term effects of consumption of GM crops unknown
● Negative environmental impacts e.g. reduction in
biodiversity, impact on food chain, contamination of
non-GM crops forming ‘superweeds’
● Late-onset health problems in GM animals
