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What are gametes?
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What are gametes?
Gametes are the sex cells of an organism, such as sperm and egg cells in humans.
What happens during fertilisation?
During fertilisation, gametes fuse to form a zygote, which is a fertilised egg cell.
How many chromosomes do human gametes contain?
Human gametes contain 23 single chromosomes, making them haploid cells.
What is the result of the fusion of gametes in sexual reproduction?
The fusion of gametes results in diploid zygotes with two alleles of each gene.
What did Gregor Mendel study in his experiments?
Gregor Mendel studied how characteristics were passed on between generations of pea plants.
What is a monohybrid cross?
A monohybrid cross is a genetic cross involving one gene with two alleles, typically one dominant and one recessive.
What is the purpose of a Punnett grid?
The purpose of a Punnett grid is to predict the probability of certain offspring displaying a certain genotype or phenotype.
What is a key feature of plants that self-pollinate?
Plants that self-pollinate can have male and female reproductive parts within the same flower, allowing for self-fertilisation.
What is meant by the terms the “P generation”, “F1 generation”, and “F2 generation” in the context of genetic crosses?
When performing a genetic cross, the P generation is the parental generation. These are pure breeding (homozygous) plants that are bred together.
The F1 generation are the offspring of the cross between the two P generation plants. These are heterozygous. These plants can be bred together.
The F2 generation are the offspring of the cross between two F1 generation plants. In a monohybrid cross, the ratio of phenotypes in this generation is 3:1.
True or False?
Genetic crosses are widely used to breed new varieties of crop or ornamental plants.
True.
Genetic crosses are widely used to breed new varieties of crop or ornamental plants.
Define the term allele.
An allele is a version of a gene, e.g. the gene that codes for eye colour may give rise to blue or brown eyes.
What is a genotype?
A genotype is the combination of alleles that an individual organism inherits.
Define the terms homozygous and heterozygous.
Homozygous is when the genotype has two of the same allele.
Heterozygous is when the genotype has two different alleles.
Define the term phenotype.
The phenotype is the observable characteristics of an organism. This can be visibly observed (e.g. eye colour) or tested for (e.g. blood type).
True or False?
The phenotype is determined only by the genotype.
False.
The phenotype is determined by the genotype, the environment, or an interaction between both.
What is codominance?
Codominance is when both alleles are expressed to an equal extent in the phenotype.
State the meaning of incomplete dominance.
Incomplete dominance is when two alleles are partially expressed, leading to a phenotype which is a blend or intermediate between the two.
True or False?
A dominant allele needs to be inherited from both parents to be expressed in the phenotype.
False.
A dominant allele only needs to be inherited from one parent to be expressed in the phenotype.
True or False?
Inheritance of flower colour in the marvel of Peru plant is an example of codominance.
False.
Inheritance of flower colour in the marvel of Peru plant is an example of incomplete dominance.
What is phenotypic plasticity?
Phenotypic plasticity is the idea that although genotype remains fixed throughout an organism's lifetime, the way that the phenotype is expressed can vary due to environmental influences.
True or False?
Phenotypic plasticity means that an organism's genotype can change during its lifetime.
False.
Phenotypic plasticity refers to changes in phenotype expression, while the genotype remains fixed throughout an organism's lifetime.
Define Single Nucleotide Polymorphism (SNP).
A Single Nucleotide Polymorphism (SNP) is the exact position where bases differ between alleles.
What is Phenylketonuria (PKU)?
Phenylketonuria (PKU) is an inherited condition caused by a recessive allele on an autosome, leading to a build-up of the amino acid phenylalanine in the body.
What is the inheritance pattern for PKU?
PKU follows an autosomal recessive inheritance pattern, requiring two copies of the recessive allele for the condition to manifest.
Define multiple alleles.
Multiple alleles refer to the existence of more than two possible allelic forms of a gene within a population.
True or False?
A person can only have two alleles for a given gene.
True.
Many genes have more than two alleles, but a diploid individual will still only inherit two of the possible alleles.
State the meaning of codominance in relation to blood groups.
Codominance in blood groups means that both the IA and IB alleles are expressed equally when present together, resulting in AB blood type.
What is the relationship between IA, IB, and i alleles for blood group?
The alleles for blood group show the following relationship:
IA and IB are codominant
IA and IB are dominant to the recessive allele, i
If one parent with type AB blood and one with type O blood have a child, what are the possible blood groups of their child?
Their child has a 50% chance of having type A blood and a 50% chance of type B blood.
This can be explained in the Punnett grid below:
IA | IB | |
i | IAi | IBi |
i | IAi | IBi |
What are the sex chromosomes?
Sex chromosomes are the chromosomes that determine the biological sex of an individual; in humans they are the X and Y chromosomes.
What are the sex chromosomes in biological females?
In biological females the sex chromosomes are XX.
What are the sex chromosomes in biological males?
In biological males the sex chromosomes are XY.
True or False?
Biological sex is determined by a single gene.
False.
Biological sex is determined by an entire chromosome pair (XX for females, XY for males), not by a single gene.
True or False?
The biological sex of a child is determined by the father.
True.
The father determines the biological sex of the child because he can pass on either an X or a Y chromosome.
What is the probability of a child inheriting two X chromosomes?
The probability of a child inheriting two X chromosomes is 1/2 or 50 %.
True or False?
The X chromosome carries fewer genes than the Y chromosome.
False.
The X chromosome carries around 16 times more genes than the Y chromosome.
What is a sex-linked disorder?
Sex-linked disorders are caused by genes that are only present on one sex chromosome and not the other.
What are the possible phenotypes for females regarding sex-linked disorders?
The three possible phenotypes for females regarding sex-linked disorders are: normal, carrier, and has the disease.
Define haemophilia.
Haemophilia is a sex-linked disease caused by a recessive allele on the X chromosome, resulting in a lack of factor VIII protein needed for blood clotting.
How should sex-linked alleles be notated in genetic diagrams?
Sex-linked alleles should be notated using an upper case 'X' or 'Y' for the chromosome, with superscript letters representing the allele. For example, XFXf represents a heterozygous female carrier for haemophilia.
If a haemophiliac father has a child with a carrier mother, what is the percentage chance their child will have haemophilia?
A haemophiliac father and a carrier mother have a 50% chance of having a child with haemophilia.
This can be shown in the Punnett grid below:
XF | Xf | |
Xf | XFXf | XfXf |
Y | XFY | XfY |
What is a pedigree chart?
A pedigree chart is a family diagram used to trace the pattern of inheritance of a specific characteristic, usually a disease, through generations of a family.
How are males and females represented in a pedigree chart?
In a pedigree chart, males are represented by squares and females are represented by circles.
What does shading or cross-hatching typically indicate in a pedigree chart?
Shading or cross-hatching in a pedigree chart typically indicates individuals that are affected by a genetic-caused trait.
True or False?
In a pedigree chart, horizontal lines between males and females show that they are siblings.
False.
In a pedigree chart, horizontal lines between males and females show that they have produced children together.
What does it typically mean if a genetic condition skips a generation in a pedigree chart?
If a genetic condition skips a generation in a pedigree chart, it typically indicates that the condition is caused by a recessive allele.
True or False?
In a pedigree chart, Roman numerals are used to indicate the age of individuals.
False.
In a pedigree chart, Roman numerals are used to indicate generations.
What is inductive reasoning in the context of pedigree charts? (NOS)
Inductive reasoning is making generalised conclusions based on specific evidence taken from a small sample, such as observing a pattern in a pedigree chart to determine if a condition is sex-linked.
Define deductive reasoning in relation to genetic inheritance. (NOS)
Deductive reasoning is making specific deductions about something unknown based on known evidence, such as deducing that a condition is caused by a recessive allele when two non-affected parents have an affected child.
What is discrete variation?
Discrete variation is variation that falls into two or more clear-cut categories with no overlap or in-between categories.
Define continuous variation.
Continuous variation occurs when there are quantitative differences in the phenotypes of individuals within a population for particular characteristics, with a range of values existing between two extremes.
What is a polygenic characteristic?
A polygenic characteristic is a trait determined by more than one gene.
True or False?
Height in humans is an example of discrete variation.
False.
Height in humans is an example of continuous variation, determined by many genetic and environmental factors.
What is the relationship between phenotype, genotype, and environment in continuous variation?
In continuous variation, phenotype = genotype + environment.
What are box-and-whisker plots used for?
Box plots, also known as box-and-whisker diagrams, are used when we are interested in splitting data up into quartiles and seeing what is happening at the low, middle, and high points of a dataset.
What are the five values needed to draw a box-and-whisker plot?
The five values needed to draw a box plot are: lowest data value, first quartile, median, third quartile, and highest data value.
What does the interquartile range represent in a box-and-whisker plot?
The interquartile range in a box plot represents the middle 50% of the data.
How are outliers defined in a box-and-whisker plot?
Outliers are data points that are more than 1.5 times the interquartile range above the third quartile or below the first quartile.
True or False?
The median in a box-and-whisker plot is always in the middle of the box.
False.
The median in a box plot will not necessarily be in the middle of the box.