D3.2 Inheritance Flashcards
How much genetic material comes from each parent?
The offspring produced have 50% of the genetic material from each parent.
Is your genetic material specific to you or not?
Your genetic makeup is specific to you and not the same as that of your sibling, even with the same parents. Unless you are a monozygotic twin (Produced from a single fertilised egg).
What happens when an individual is sexually matured?
Cells within specialised organs called gonads will start to undergo a certain kind of cell division called meiosis. The gonads contain cells whose nuclei have pairs of chromosomes. The cells divide twice during meiosis and the unique cells produced are given the term gametes. These are known as haploid (n) as they have only one copy of each chromosome from one of the parents.
What is special about gametes?
The gametes are highly specialised with specific features. On their own, these gametes cannot generate a new individual. Two gametes (one from the male parent and one from the female parent) fuse together to form a diploid (2n) zygote that now contains an equal amount of genetic information from both parents.
What is hermaphroditic?
Hermaphroditic is when the male and female gametes are often present in the same plant e.g. pea plant.
Who was George Mendel? And why is he famous?
A monk named Gregor Mendel (1822–84) from an area now found in the Czech Republic, conducted numerous plant-breeding experiments over many years using the humble pea (Pisum sativum). He observed flower colour along with the texture and colour of pea seeds and pods. His experiments are so important that he is often referred to as the ‘father of genetics’.
What was Mendel’s experiment?
In his experiments, Mendel crossed many pea plants by selecting the pollen from one plant and brushing it onto the stigma of another plant. He was able to first observe and later predict the inheritance of different pea flower and pea seed traits. For example, he showed that when true-breeding parents for traits such as round seeds were bred with true-breeding parents for wrinkled seeds, they would result in offspring that produced only one form of these traits (e.g. round seeds).
What is the P generation?
Parent generation of a genetic cross. (Parental generation)
What are offspring called in genetic crossing?
The offspring are called the filial (F) generation.
What is F1 generation?
F1 are the offspring from the P generation (First generation).
What is F2 generation?
If two members of the F1 generation are subsequently bred together, this would give rise to the F2 generation which would then possess some physical characteristics not seen in the F1 generation. ( F2 are the offspring produced from crossing F1 parents)
How can genetic breeding be linked to solution for UN SDG 2 zero hunger and climate change?
Genetic breeding experiments between two related species are commonly used to generate new varieties of crops. Specific individuals can be carefully selected to ensure that the offspring have desired characteristics. Scientists around the world are focused on breeding plants that are able to cope with climate change, extreme weather, drought or flooding.
What are homologous chromosomes?
A pair of chromosomes of the same type (one comes from the mother and one comes from the father).
What is a gene?
Along the length of the chromosome are stretches/ a segment of DNA that codes for a specific protein.
What is the relationship between location and the gene on homologous chromosomes?
These genes are in identical positions on each of the chromosomes and so an individual will therefore have two copies of the gene (one from each parent).
Do genes need to be identical on the homologous chromosomes?
However, the two genes may differ from each other by a few bases. These different forms of a gene are called alleles.
What is an allele?
A variant or version of a gene.
What happens when the alleles combine?
This allele combination is called the genotype.
What is a genotype?
The specific set of DNA that an organism possesses.
What is it called when a gene has two identical alleles?
Homozygous
What is homozygous?
Both alleles for a trait are the same, for example, FF or ff.
What is it called when the two alleles are different from one another?
Heterozygous
What is heterozygous?
The alleles for a trait are different e.g. Ff.
How are genotypes determined?
Genotypes can be hard to determine but some physical traits are easily visualised and are caused by the genotype an individual possesses e.g. hitchhikers thumb.
What is a phenotype?
The outward expression of the combination of the alleles along with the influence of environmental. (Physical traits and characteristics of a cell or organism)
Are phenotypic traits always determined by environment or genotype?
Some traits, like our skin colour, are a combination of both genetics and environment; in this case, how much we expose our skin to the sun.
Can genes effect the way you taste?
Yes, the ability to taste the bitter chemical is controlled by one gene called TAS2R38 which codes for a protein for a taste receptor on the tongue. There are two common forms of the allele: one allele is the ‘tasting allele’ and one the ‘non-tasting’ allele.
What is a dominant allele?
A dominant allele masks the presence of the recessive allele.
What is a recessive allele?
A trait that is only expressed when it is in the homozygous form.
What is homozygous dominant?
Both alleles for a trait are dominant, for example, FF.
What is homozygous recessive?
Both alleles for a trait are recessive, for example, ff.
What is phenotypic plasticity?
The ability of an organism to express different phenotypes depending on the abiotic or biotic environment
This involves regulatory genes that switch on structural genes given the appropriate stimulus.
What does phenotypic plasticity allow an individual to do?
It allows individuals with the same genome to adapt when exposed to different environmental conditions. These changes may involve an alteration in behaviour, physiology or morphology. This is not caused by changes in the genotype and these changes do not even need to be permanent; the changes might be reversed during the individual’s lifetime depending on the situation.
Why is phenotypic plasticity important?
Phenotypic plasticity is important as a means to increase the chances of survival in a changing global climate.
What is an example of phenotypic plasticity?
An example of this phenotypic plasticity is the seasonal polyphenism of the butterfly Bicyclus anynana. When it is cooler, the adults take on the form of ‘dry-season’ adults that live for a longer time and breed at the end of the season. Their wing patterns are similar to dry foliage so that they can escape predators. However, when the weather is warmer, the adults look more like ‘wet-season’ adults. These have a shorter life span but breed many times during this season. Their wing patterns have distinctive eye spots that prevent predation. As the seasons change, so does the butterfly’s physical form.
What is a recessive genetic condition?
A recessive genetic condition means the individual would need to be homozygous recessive with two copies of the recessive allele to have the trait. The presence of one correct allele is sufficient to generate the functioning enzyme and results in a healthy individual.
What is an example of a recessive genetic condition?
One such recessive disorder is phenylketonuria or PKU. PKU is caused by a mutation in a gene on chromosome 12, This gene codes for an enzyme used in metabolism called phenylalanine hydroxylase (PAH) that converts the amino acid phenylalanine (Phe) into tyrosine (Tyr). In a child that is homozygous recessive for this allele, the Phe in the cell is not broken down and so toxic levels build up.
What the symptoms of PKU?
The baby may initially seem healthy but within a few months, symptoms can develop, such as a musty odour from the skin and urine, fair skin, eczema, seizures, tremors and hyperactivity.
How is PKU tested?
In most countries around the world, babies are tested for PKU at 1–2 days of age. A simple heel stick gives a drop of blood that can be tested on a filter paper for the Phe:Tyr ratio. If the test reveals a high level of Phe, then further testing is conducted.
What happens if PKU is not treated? And what is treatment?
If the condition is left untreated, brain damage can occur. Unfortunately, there is no quick treatment, but this condition can be well managed if a life-long dietary plan that keeps protein levels low is maintained, along with frequent blood tests.
