Genetic Crosses Flashcards
What are gametes?
Haploid cells that are capable of fusing with each other. They are formed by meiosis.
Define fertilisation.
The joining of a haploid male gamete with a haploid female gamete to form a diploid zygote.
What are somatic cells?
Non-sex cells (not gametes)
What are alleles?
Different variants of a gene
What is a locus?
The place where a certain gene is positioned on a chromosome
Define autosomes.
Non-sex chromosomes
What are sex chromosomes?
The X and Y chromosomes
What gene does the Y chromosome contain that determines sex?
The SRY gene
True or False: The Y chromosome carries sex-linked conditions.
False
What is a dominant allele?
An allele that will be expressed even in the presence of a recessive allele
Define a recessive allele.
An allele that is not expressed in the presence of a dominant allele
What does genotype refer to?
Genetic make-up, i.e. the set of gene variants the organism has
What is phenotype?
Physical make-up, i.e. the set of physical traits that are expressed in the organism
What is progeny?
What offspring are produced during a genetic cross
Define homozygous.
Having two copies of the same allele
What does heterozygous mean?
Having two different alleles of a gene
What is incomplete dominance?
The expression of alleles is not masked leading to an intermediate phenotype
Who is Gregor Mendel?
Father of genetics. He bred garden peas to show how genetic crosses work.
What is the Law of Segregation?
Inherited characteristics are controlled by pairs of alleles that separate during gamete formation.
Define the Law of Independent Assortment.
When gametes are formed, either member of a pair of alleles is equally likely to join with either member of another pair of alleles.
What does linkage refer to in genetics?
Genes are located on the same chromosome
What are sex-linked genes?
Genes located on the sex chromosomes
Provide examples of sex-linked diseases.
- Haemophilia
- Colour blindness
What types of plants did Gregor Mendel use in his experiments?
Tall and short plants, round and wrinkled seeds
These traits were used to study inheritance patterns.
What was the result of crossing a pure tall plant with a pure short plant?
All offspring were pure tall
This demonstrated that the tall trait is dominant.
What was the outcome of crossing a plant that produced smooth seeds with a plant that produced wrinkled seeds?
All offspring were smooth
This indicates that the smooth seed trait is dominant.
What was the ratio of smooth to wrinkled seeds in the second generation offspring?
3:1 ratio
This ratio applies to all traits in the second generation offspring.
Fill in the blank: All traits had a _______ ratio in the 2nd generation offspring.
3:1
What does the term ‘dominant gene’ refer to in Mendel’s experiments?
A gene that masks the presence of another gene
In Mendel’s case, the tall plant and smooth seed traits were dominant.
What method did Mendel use to produce the second generation of plants?
Self-fertilization
This allowed him to observe the inheritance patterns of traits.
