dna & inheritance (new) Flashcards
sexual reproduction
when male and female gametes fuse
Recall the male and female gametes found in plants.
Pollen and Egg Cells
Which process are gametes formed?
Meiosis
What happens to the number of chromosomes during meiosis?
They halve in number (23 Chromosomes)
What happens to the number of chromosomes during fertilisation?
They are restores to the full number (46 Chromosomes)
What is formed after cells in reproductive organs divide by meiosis?
Gametes
How many times does the cell divide to form 4 gametes?
The cell divides twice to form four gametes.
What needs to happen for variation to give a survival advantage by natural selection.
Environment Changes.
State way humans can increase food production by natural selection.
Use Selective Breeding.
How do malarial parasites reproduce in humans?
In humans = Asexually
How do malarial parasites reproduce in mosquitos?
In mosquitos = Sexually
How do fungi reproduce
By Spores becoming new fungi when they land in a suitable place
2 types of spores?
asexually produced - genetically identical
sexually produced - variation
Name the plant which reproduces asexually. and how
Strawberry plants produce runners which are stems that grow horizontally on the surface of the soil which grows new identical plants along it
Name the plant which reproduces by bulb division. and explain what it is
Daffodils. new bulbs form on the main bulb and divide off each new bulb can form into a new identical plant
Why is DNA classed as a polymer?
DNA is made up of two strands of nucleotides in a double helix
What is a Gene?
A gene is a small section of DNA on a Chromosome.
In DNA, what does each nucleotide contain?
Sugar and phosphate group with a base attached to the sugar.
Name the bases found in DNA.
Adenine, Cytosine, Guanine & Thymine.
How many bases in DNA are needed to code for an Amino Acid?
3 bases = an Amino Acid (also a Gene).
What happens when the order of bases are changed in DNA?
A different protein is made.
DNA is polymer, what is the monomer?
Nucleotides.
What happens to enzymes when the order of bases are changed in DNA?
Leads to change in shape of the enzyme and the active site.
How do genetic variants influence phenotype in non-coding DNA?
By altering how genes are expressed.
Which organelle in the cell synthesises proteins?
Ribosomes.
Which molecule adds specific amino acids to add to a growing protein chain?
Carrier Molecules.
Give 3 examples of proteins found in the body.
Enzymes, Hormones & Collagen.
How often do mutations occur?
continuously and spontaneously
What happens when a mutation leads to a change in the shape of an enzyme or a structural protein?
An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.
What is a function of Non-Coding parts of DNA?
Can switch genes on and off. variations in them can affect how genes are expressed
Define the term Allele.
Different forms of the same gene.
Define the term Homozygous.
When an organism has two alleles that are the same for an inherited characteristic
Define the term Heterozygous.
When an organism has two alleles that are different for an inherited characteristic.
Define the term Genotype.
The genetic makeup of an organism, controls the phenotype.
Define the term Phenotype.
Characteristics expressed by the organism.
Name the 2 characteristics controlled by a single gene.
Fur colour in mice and red-green colour blindness in humans.
How many genes are required in most characteristics?
not exact value
Multiple Genes.
State the cause of inherited disorders.
Inheritance of certain alleles.
What is Polydactyly and what type of allele is it caused by?
Having extra fingers or toes and is caused by a dominant allele.
What is Cystic Fibrosis and what type of allele is it caused by?
A disorder of cell membranes and is caused by a recessive allele.
what happens when a protein chain is complete
when a chain of ammino acids has been assembled it folds into a unique shape which allows protein to perform a specific function
3 types of mutation
- insertions
- deletions
- substitutions
PGD
- method of genetic embryo screening
- during ivf u remove 1 cell from each embryo and analyse its genes (pgd)
- embryos with healthy alleles reimplanted
CVS
- method of embryo genetic screening
- usually between 10 -13 weeks
- take a sample of cells from the placenta and analyse the genes
- if embryo has an inherited disorder parents can decide whether or not to terminate
arguements for embryo screening
- alleviates suffering
- treating disorders is expensive
- during ivf most embryos are destroyed anyway PGD just ensures chosen one is healthy
- with cvs parents dont HAVE to terminate
arguments against embryo screening
- designer babies
- implies ppl with genetic problems are undesirable - increases prejudice
- in pgd rejected embryos are destroyed - could have been a human life
- in cvs parents may terminate a pregnancy they would have otherwise kept
expensive
How many PAIRS of chromosomes to human body cells have?
23 pairs (46 in total).
What do the first 22 chromosomes control.
Characteristics.
State the pairs of chromosomes which determine a human’s sex.
“Females = XX
Males = XY”
How could we influence the development of the phenotype?
Change in genotype or environment.
What 3 reasons may there be a cause for variation in a population?
”* The genes they have inherited (genetic causes)
* The conditions in which they have developed (environmental causes)
* A combination of genes and the environment.”
How often does a mutation lead to a new phenotype?
Very rarely.
Define Evolution.
A change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species.
What does natural selection of variants give rise to?
Phenotypes best suited to their environment.
Give an example of a useful characteristic in selective breeding.
”* Disease resistance in food crops.
* Animals which produce more meat or milk.
* Domestic dogs with a gentle nature.
* Large or unusual flowers.”
Define Genetic Engineering.
A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
Why are Bacterial cells genetically engineered?
To produce useful substances such as human insulin to treat diabetes.
State the benefits of GM crops.
- Resistant to insect attack & herbicides.
- GM crops have increased yield.
- more nutrients - i.e golden rice
State the disadavtages of GM crops.
“Negative effect on populations of wild flowers and insects.
Some people feel the effects of eating GM crops on human health have not been fully explored.”
State the steps of Genetic Engineering.
“In Genetic Engineering:
* Enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus.
* The vector is used to insert the gene into the required cells.
* Genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics.”
tissue culture
a few plant cells are put in a medium with growth hormones like auxin and grow new plants
- quick and little space
- preserves endangered species
Why was Darwin’s theory of evolution only gradually accepted?
”* The theory challenged the idea that God made all the animals and plants that live on Earth
* There was insufficient evidence at the time the theory was published to convince many scientists
* The mechanism of inheritance and variation was not known until 50 years after the theory was published.”
Name the scientist who proposed that changes that occur in an organism during its lifetime can be inherited.
lamarck
Name the scientist who is best known for his work on warning colouration in animals and his theory of speciation.
wallace
Name the scientist who is best known for his observation that inheritance of each cahracteristic is determined by “units”.
mendel
Define the term Fossils.
The ‘remains’ of organisms from millions of years ago, which are found in rocks.
How are Fossils formed?
”* From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
* When parts of the organism are replaced by minerals as they decay
* As preserved traces of organisms, such as footprints, burrows and rootlet traces.”
Why cannot scientists be certain about how life on Earth began.
Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity.
What can we learn from Fossils?
How much or how little different organisms have changed as life developed on Earth.
Name a bacterial strain which is resistant to antibiotics.
MRSA.
How can we reduce the rate of development of antibiotics strains?
”* Doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
* Patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains
* The agricultural use of antibiotics should be restricted.”
Recall the catagories which Linnaeus classified living things.
Kingdom, phylum, class, order, family, genus and species.
Why did new models of classification progress?
Evidence of internal structures became more developed due to improvements in microscopes, and the understanding of biochemical processes progressed.
State the three domains found in Carl Woese system.
Archaea, Bacteria & Eukaryota.
embryo transplant
- sperm used to artificially fertilise an egg cell
- embryo that developes is split many times to form clones
- cloned embryos implanted into different host mothers
adult cell cloning
- remove nucleus of unfertilised egg cell
- replace with nucleus taken from adult cell
- electrically stimulate egg cell to divide to form embryo
- implant in host mother
pros of cloning
- used to preserve endangered species
- quickly get lots of ideal offspring with desired characteristic
- study of animal clones could lead to greater understanding of embryo development , aging and age related disorders
cons of cloning
- reduced gene pool
- cloned animals may not be as healthy
