CB3: Genetics Flashcards
What are the male and female gametes in an animal?
Egg and sperm.
What are the male and female gametes in plants?
Egg and pollen.
Describe the process of meiosis.
The DNA is copied. The cell divides twice to form four gametes, each with a single set of chromosomes. All gametes are genetically different from each other.
What is a gene?
A section of DNA which codes for a protein.
What is an allele?
A version of a gene.
What do dominant and recessive mean?
The dominant allele will take priority over recessive genes in the phenotype.
What does homozygous mean?
Both alleles from each parent are the same.
3 advantages of sexual reproduction:
Variation, increase in food production, a change in environment could be survived due to variation.
What does heterozygous mean?
Both alleles from each parent are different.
What is the genotype?
The complete set of genetic material for an organism.
3 advantages of asexual reproduction:
One parent is required, takes less time, the offspring are identical.
3 examples of organisms that can produce both sexually and asexually.
Fungi, plants, malaria parasites.
What was one of Mendel’s observations when breeding plants?
Characteristics of an organism are determined by factors within that organism.
Describe the basic structure of DNA.
Polymer made up of two strands forming a double helix. Each strand has a sugar-phosphate backbone with a sequence of bases attached.
When did Mendel make his observations?
1865.
How many chromosomes do human body cells have?
23 pairs (46 total).
When was the behaviour of chromosomes during cell division first observed?
The late 1800s.
What are the 4 bases of DNA and how are they paired?
Adenine + Thymine and Guanine + Cytosine
What are the monomers of DNA called?
Nucleotides.
How were Mendel’s observations and the observation of chromosome behaviour linked?
In the early 20th century, it was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways. This led to the theory that the ‘units’, now called genes, were located on chromosomes.
How does DNA code for a protein?
The sequence of bases in the DNA molecule determines the sequence of amino acids in the protein molecule.
When was the structure of DNA discovered and who was it by?
1953, by Watson and Crick (and Franklin).
What is an inherited disorder?
An inhereted disorder is when a disorder (such as ginger) is passed down genetically through inheritance.
Describe how a protein is synthesised.
A template of the DNA sequence is made.
The ribosomes read the template and construct a protein by joining together amino acids.
When the chain is complete it folds up into the specific shape of the protein.
Give two examples of inhereted disorders.
Cystic fibrosis, Hungtington, Haemophilia, Sickle cell disease, Down syndrome, Type I diabetes.
How can a change in DNA structure lead to a change in the protein?
May lead to change in the amino acid sequence. This may affect the shape of the protein as it will fold differently. The protein may no longer be able to perform its function.
Is the allele for polydactyly dominant or recessive?
Dominant.
Is the allele for cystic fibrosis dominant or recessive?
Recessive.
Do all mutations alter the function of a protein?
Most do not change the protein, or affect its appearance or function.
List (in order) the 7 taxonomic groups.
Kingdom, phylum, class, order, family, genus and species.
Why have new models of classification been proposed?
Microscope technology has improved, allowing us to better observe the structures inside cells. Our understanding of biochemical processes has also progressed.
Describe the “three domain system” developed by Carl Woese.
Organisms are divided into:
Archaea (primitive bacteria usually living in extreme environments)
Bacteria (true bacteria)
Eukaryota (which includes protists, fungi, plants and animals)
Outline Darwin’s theory of evolution by natural selection.
There is variation between members in a population. More offspring are produced in each generation than there are resources for (so not all will survive). Certain characteristics may give an organism an advantage, so they are more likely to survive and reproduce , passing the genes for that characteristic on to the next generation. Over time, this characteristic will become more common within the population.
In what year was “On the Origin of Species” published?
1859.
Why were Darwin’s ideas only gradually accepted?
Evolution by natural selection could not be observed in action (it takes a long time). Many people felt it contradicted their religious beliefs.
What was Jean-Baptiste Lamarck’s theory of evolution?
Organisms gain characteristics over their life time (e.g a giraffe stretches its neck to reach the high leaves) and then these changes are passed onto their offspring.
Why do we not accept Jean-Baptiste Lamarck’s theory today?
We now know this is not the case as environmental variation is not inherited.
What process did Alfred Russel Wallace do pioneering work on?
Speciation.
Describe the steps which give rise to new species.
Speciation occurs when two groups of organisms (of the same species) become isolated from each other. Members of one group are prevented from breeding with members of the other group. Over time, the two groups become so genetically different that they would no longer be able to breed together to produce fertile offspring: therefore, two new species have been formed.
What evidence exists to support Darwin’s theory of evolution?
Fossils and antibiotic resistance to bacteria.
What is a fossil?
Fossils are the ‘remains’ of organisms from millions of years ago, which are found in rocks.
Give 3 ways in which fossils may be formed.
From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent.
When the parts of the organism are replaced by minerals as they decay.
As preserved traces of organisms, such as footprints, burrows and rootlet traces.
Why is the fossil record incomplete for early life forms?
Many early life 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. This is why scientists cannot be certain about how life began on Earth.
What can we learn from fossils?
We can learn from fossils how much or how little different organisms have changed as life developed on Earth.
When does extinction occur?
Extinctions occur when there are no remaining individuals of a species still alive.
What factors can contribute to the extinction of a species?
Destruction of wild habitats, introduction to invasive species, climate change, hunting, illegal trafficking, over harvesting.
