B5.1: Inheritance Flashcards
What is a phenotype?
The appearance of an organism
What is variation?
Differences within a species
What are the 2 causes of variation?
Environmental variation
Genetic variation
What is genetic variation?
Genetic material inherited from parents
What is environmental variation?
The environment in which you live in
What is an example of a characteristic that is affected both by environmental and genetic variation?
Height - if your parents are tall you are more likely to be tall BUT if your diet is very poor you may not grow to your full potential height
What are examples of characteristics caused by genetic variation alone?
Eye colour
Blood group
What is discontinuous variation?
Can only result in specific values that fall into distinct groups.
How can discontinuous variation be represented?
Bar charts
What is continuous variation?
Can take up any value within a range. A characteristic can be any value between a minimum and maximum.
How can continuous variation be represented?
Histogram
What are the causes of continuous variation?
Genetic and environmental
What are the causes of discontinuous variation?
Genetic
What are examples of continuous variation?
Height
Weight
What are examples of discontinuous variation?
Gender
Eye colour
How many genes are continuous variation controlled by?
Multiple genes
How many genes are discontinuous variation controlled by?
One (or few) gene(s)
What is asexual reproduction?
Creating a genetically identical copy of the parent, often ocurring through the process of mitosis
Who performs asexual reproduction?
Bacteria
Some plants
Some animals
What are some examples of plants who reproduce asexually?
Potato plants
Daffodils
What are advantages of asexual reproduction?
Faster reproduction
If parent is well adapted to the area, offspring will have the exact same genetic info
What are disadvantages of asexual reproduction?
No genetic variation
Harmful mutation will pass onto offspring because it’s an exact clone
What is sexual reproduction?
Requires 2 parents as genetic info is taken from both of them. Results in variation. Performed by meiosis
What are advantages of sexual reproduction?
Genetic variation within the population
More likely that offspring will be able to survive from environmental changes: evolution —> species become better adapted
What are disadvantages of sexual reproduction?
Takes more time/energy: fewer offspring
2 parents needed - problem if individuals are isolated
What does sexual reproduction produce?
Sex cells: gametes
Gametes fuse together in fertilisation. Egg develops into offspring
What are diploid cells?
Two complete sets of each chromosome (46)
What are haploid cells?
One set of chromosome (23)
What is a zygote?
Fertilised egg where 2 haploid cells join together during fertilisation
What is a genome?
The entire genetic material of an organism
What is cell division?
Caused by meiosis
Results in 4 haploid cells being produced from one diploid parent cell
How many times does the nucleus split in meiosis?
2 times
What are alleles?
Different forms of a gene
What is a dominant allele?
A form of a gene that is fully expresed. Only one copy is needed for the characteristic to be expressed
What is a recessive allele?
The gene that will not be expressed if in the presence of a dominant gene.
Two recessive alleles are needed for the characteristic to be expressed
Suppose B and b are the alleles for a recessive genetic condition. What will the homozygous dominant outcome be?
BB
Suppose B and b are the alleles for a recessive genetic condition. What will the homozygous recessive outcome be?
bb
Suppose B and b are the alleles for a recessive genetic condition. What will the heterozygous outcome be?
Bb
What is homozygous?
An organism that has two identical alleles for a characteristic
What is heterozygous?
An organism that has 2 different alleles for a characteristic
What is a genotype?
The alleles present for a particular gene make up
What is a gene?
A short section of DNA that contains instructions for a protein
What are chromsomes?
These are made up of DNA and are found inside the nucleus. Each one contains a number of genes. Genetic info is carried on them
What is the 23rd pair of chromosome?
Which pair of chromosomes determines the sex
XY
Male sex chromosomes
XX
Female sex chromosomes
What are mutations?
Any change in the DNA base sequence
What is a punnet square?
A chart that shows all the possible combinations of alleles that can result from a genetic cross
What can increase chances of mutations?
Benzene
Ethanol
Ionising radiation
What is a genetic variant?
Different version of the gene an allele
How does mutations affect phenotype?
Most of the time, it doesn’t. But sometimes it does
What are examples of mutations that affect phenotype?
Cystic fibrosis
Sickle cell anaemia
Huntingtons
Albanism
What is an example of a disease caused by mutations?
Cancer
Why are a few mutations beneficial?
They cause resistance to antibiotics in bacteria cells
This increasess bacteria survival chance, helpful for the bacteria
What happens to DNA bases in a mutation?
Bases may be added, changed or deleted. The order of amino acids may be assembled differently, meaning the wrong protein is created
If the protein is an enzyme, active site may be changed, meaning it can no longer bind to the substrate. This means certain metabolic reactions won’t be able to occur
What did Gregor Mendel discover? When?
1866
Introduced the concept of hereditary
What did Friedrich Miescher discover? When?
1869
Discovered DNA
What did Oswald Avery discover? When?
1944
Genes are made of DNA
What did Erwin Chargaff discover? When?
1950
DNA contains equal amounts of ACGT
What did Wilkins and Franklin discover? When?
1952
Imaged DNA crystals using x-rays
What did Aston and Crick discover? When?
1953
Published description of double helix
What was discovered in 2003?
Scientists sequenced around 24,000 genes in the human genome
What current research is going on? From when?
2003+
Cure genetic diseases
How many genes are phenotypic features a result of?
Most phenotypic features are the result of multiple genes rather than single gene inheritance
