biology topic 6 Flashcards
genetic material is made from what
DNA
what is DNA made from
DNA is a polymer made from many nucleotides/monomers
what is a polymer
A polymer is a large molecule made from many smaller molecules called monomers.
what is the shape of DNA
a double helix.
how is DNA arranged
DNA is arranged in structures called chromosomes inside a cell’s nucleus.
what are genes
A gene is a small section on a
chromosome. Each gene
codes for a particular
characteristic (sequence of
amino acids, to make a
specific protein.)
how many pairs of chromosomes do humans have
Humans have 23 pairs of chromosomes.
describe the structure of a nucleotide
Nucleotide = Phosphate binds to Sugar binds to base (Bases = A, T, C, G)
Complementary pairing = A+T, C+G
proteins make up what
- Enzymes
- Hormones
- Antibodies
- Structural
what codes for partucular amino acids
Three bases is the code for a particular amino acid.
The order of the bases controls the order in which amino acidsare
assembled to produce an individual protein.
where are proteins made
but proteins are made in the cytoplasm on
ribosomes.
describe making new proteins (protein synthesis)
- Part of the DNA unravels.
- Enzymes make a copy of the DNA strand. This is
called mRNA in a process called transcription - mRNA moves out of the nucleus into the cytoplasm.
- The mRNA travels to the ribosome in the cytoplasm.
- Ribosomes translate each set of 3 bases into amino acids according to the mRNA template.
- Amino acids are found in the cytoplasm. The correct amino acid for each set of 3 bases is brought to the ribosome by a carrier molecule.
- A long chain of amino acids form. Their specific order forms a specific protein.
what are the three types of mutation in DNA
Substitution
Insertion
Deletion
describe substitution mutations
one base gets substituted by another – most of the time makes NO
DIFFERENCE to the protein formed
describe insertion mutations
A base is inserted into DNA.
Affects EVERY subsequent amino acid from the DNA molecule. Results in a non-functioning protein
describe deletion mutations
A base is deleted from DNA.
Affects EVERY subsequent amino acid from the DNA molecule. Results in a non-functioning protein
what are causes of mutations
Faulty copying of DNA
Chemical agents, (mutagens/carcinogens)
Ionising radiation
what are the effects of mutation
- A mutation CAN change the base
- Leads to a different sequence of amino acids being translated
- Leads to a different protein being formed
- Active site changes shape
- Substrate can no longer fit to active site
- Enzyme can no longer catalyse reactions
Coding strands of DNA do what
code for proteins
Non coding parts of DNA does what
can switch genes on or off in a
cell
Mutations in the non coding DNA may do what
DNA may affect how
genes are expressed(translation)
what is the genome of an organism
The genome of an organism is defined as the entire genetic material of that organism.
why is understanding genomes important
❑ Find genes linked to different types of disease
❑ Understand and treat inherited disorders
❑ Trace human migration patterns.
what is Sexual reproduction
joining of male and female gametes.
what are gametes
sex cells
(humans = sperm/egg cell) (plants = pollen/egg)
what is Asexual reproduction
Asexual reproduction involves only one parent. There is no fusion of gametes. No mixing of genetic information occurs. All offspring are genetically identical (called clones).Only mitosisis involved.
meiosis vs mitosis
Meiosis leads to non identical cells being formed.
Mitosis leads to identical cells (clones) being formed.
Advantages of sexual
reproduction
Variation occurs in the offspring (due to having gametes)
Better chance surviving by
natural selection.
Advantages of asexual
reproduction
More efficient (Time and Energy)
– Don’t need to find a mate
Many identical offspring can be
produced
what is Meiosis
This is the process a cell goes through to producegametes:
describe the meiosis process
DNA Replicates/ Duplicates
cell divides
Chromosomes from 1 cell mix with the chromosomes from another cell leading to genetic variation
cells divide again
Forms 4 genetically
different cells (sperm
or egg cells. No other cells)
what are alleles.
Different forms of the
same gene
The alleles which are present in your body are known as the what
the genotype.
The actual characteristics seen are called the what
the phenotype.
Most genes have two possible allele variations which are known as what
dominant or recessive.
Dominant alleles are represented by what
capital letter e.g. B
Recessive alleles are represented by what
lower case letter e.g. b
what is Homozygous
Where you have 2 of the same alleles (BB or bb)
what is Heterozygous
Where you have 2 different alleles (Bb
A recessive allele is only expressed if what condition is met
A recessive allele is only expressed if two copies are
present and therefore no dominant allele present.
How many chromosomes do humans have in their cells
46
How many chromosomes are in sperm/egg cells
23
In terms of x and y alleles what makes males and females
Male - XY
Female - XX
What does Polydactyly cause
Polydactyly causes extra fingers/toes. Caused by a dominant allele.
What is Cystic Fibrosis
Cystic Fibrosis causes excess mucus to be produces.
Caused by a recessive allele.
Red green colour blindness caused by a recessive
mutation on an X chromosome
Males more likely to be affected – Why?
Males only have 1 X chromosome
If it is mutated then male would be colour blind Females have 2 X chromosomes If 1 if mutated, female would be fine 2 have to be mutated to get the disorder
Why are We are able to describe a phenotype but cannot write down a genotype
because
more than one gene isinvolved.
What are advantages of embryo screening
prevent having child with the disorder/future suffering
reduce incidence of the disease
embryo cells could be used in stem cell treatment
What are disadvantages of embryo screening
Possible damage to embryo (during testing for cystic fibrosis / during operation)
Expensive
Embryo can’t consent
May lead to infection in mother
Can lead to false negatives
What is gene therapy
replacing faulty alleles with working ones
What are advantages of gene therapy
Reduce suffering
What are disadvantages of gene therapy
Expensive, not tested well enough
What is a dominant disorder
A dominant disorder is one that is caused by the presence of ONE dominant allele
What is a recessive disorder
A recessive disorder is one that is caused by the presence of TWO homozygous recessive alleles
Screening of the embryo (or fetus) can be completed from how many weeks of pregnancy
10 weeks
What is one of the risks of embryo screening
There is a risk of miscarriages
Describe how embryo screening is done
A fine needle is passed through the abdomen into the
uterus and a small piece of the developing placenta is
removed.
This is analysed to see if alleles that cause polydactyly,
cystic fibrosis or other genetic disorders are present.
This testing is usually only done when there is a family
history of the disorder. Screening is costly and not
100% reliable.
What might some causes of variation be
differences in the genes
differences in the environmental
a combination of both
Describe natural selection
• New characteristics arise from genetic
mutations
• Organisms with characteristics that are better
adapted for survival will survive,
• reproduce
• pass on their useful characteristics on to
future generations.
The theory of evolution by natural selection states what
that all living
things have evolved from simple life forms that developed over3
billion years ago.
What did Charles Darwin work on
natural selection and evolutio
What did Alfred Russel Wallace work on
warning colouration,theory of speciation.
What is Jean-Baptiste Lamarck’s: theory of evolution
changes which occur in an
organism during its lifetime can be inherited. - Incorrect
GregorMendel proposed the ideas of what
proposed the ideas of ‘units’ that are passed on to descendants
unchanged. Based on experiments done on pea plants
Why was Darwin’s theory of evolution not accepted at first:
Challenged the idea that God made all life
Insufficient evidence
Mechanism of inheritance not known
Describe speciation
• A species is
separated due to a
physical barrier
• Environment of
each part of the
island changes
• Animals adapt to
new environment
• Eventually become
new species over
millions of years
What is extinction
No individuals of a species are left alive
What can extinction be caused by
Environment changes too quickly (destruction of habitat)
New predator
New disease kills them all
Cant compete for food/habitat
Catastrophic event (volcanic eruption, asteroid strike)
why can scientists never be certain about how life began
1.Early life forms were often soft bodied and so few tracesremain.
- Most organisms do not become fossilised as conditions are rare.
- We are still discovering fossils which give us more information.
4.Traces are often destroyed by geological activity like earthquakes, volcanic eruptions, formation of mountain range and erosion.
Describe the process of genetic engineering
Identify the desired gene
Remove the gene from the DNA
using enzymes
Cut open the plasmid from bacteria OR the DNA from an organism using enzymes
Insert the removed gene using
enzymes again
Clone the organism to produce lots of copies
What are advantages of genetic engineering
Useful characteristics passed on
What are disadvantages of genetic engineering
Reduces the gene pool so one disease can kill all
What are the advantages of genetic engineering in plants
Bigger crop yields
Frost resistant,
Pest resistant,
Disease resistant,
Longer shelf life
What are the disadvantages of genetic engineering in plants
Do not know the long term
effects on wild life and human
health
GM crops which produce their
own pesticide may kill insects
which are needed to pollinate
other plants.
Describe how adult cell cloning is done (cloning an animal)
A skin cell is taken from Sheep A.
Unfertilised egg cell is taken from Sheep B.
Nucleus is removed from both cells
Nucleus from sheep A is
fused with empty egg cell
of sheep B.
An electric shock stimulates the egg cell to divide.
Embryo is implanted into
adult female sheep to
continue its development.
What are the disadvantages of cloning
Cloning is expensive and some people feel it is unethical to remove the embryo from its mothers uterus and split it apart.
What are two methods for client plants
Tissue Culture and Cuttings
How is tissue culture used to clone plants
Small piece of tissue is taken from a plant Grown on agar with the right balance of nutrients and hormones.
Disadvantages: Expensive
Advantages: Preserve rare plants
How are cuttings used to clone plants
Remove a part of the plant, plant it in soil add
rooting powder/auxin
Simple, Cheap
How does antibiotic resistant bacteria occur
mutation occurred giving resistance
only resistant bacteria survive
these bacteria reproduce
resistant bacteria pass on the gene / allele
leading to a new population of resistant bacteria
What is antibiotic resistant bacteria caused by
Overuse of antibiotics
What are the levels of classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
