Genetics, populations, evolution and ecosystems

What is a dihybrid cross?

A genetic cross involving two characteristics inherited from two different genes, each having different alleles.

What is the expected phenotypic ratio of a dihybrid cross?

The expected phenotypic ratio is 9:3:3:1.

How many blood groups can result from the immunoglobulin gene variations?

There are four different blood groups: A, B, AB, and O.

What are multiple alleles?

Genetic situations where a gene has more than two allele variants within a population.

What genotypes represent blood type A?

Iᴬ Iᴬ or Iᴬ Iᴼ

What genotypes represent blood type B

Iᴮ Iᴮ or Iᴮ Iᴼ

What genotypes represent blood type AB

Iᴬ Iᴮ

What genotypes represent blood type O

Iᴼ Iᴼ

What is the allele for round shaped seeds?

The allele for round shaped seeds is R, which is dominant.

What is the genotype for homozygous recessive for seed shape?

The genotype for homozygous recessive for seed shape is rr.

What does the notation 'RrGg' represent?

'RrGg' represents a heterozygous genotype for both seed shape and seed color.

What is the difference between monohybrid and dihybrid crosses?

Monohybrid crosses involve one pair of alleles, while dihybrid crosses involve two pairs of alleles.

What are the two sex chromosomes in mammals?

X and Y chromosomes.

What is the usual sex chromosome combination for males and females?

Males: XY, Females: XX.

What does a Punnett square show regarding offspring probability?

The probability of having male or female offspring is 50%.

What are sex-linked characteristics?

Characteristics coded for by genes found only on sex chromosomes.

Which chromosome carries fewer genes, X or Y?

Y chromosome.

What is an example of a condition that is X-linked?

Colour blindness and haemophilia.

What does it mean for a male to have one allele of an X-linked gene?

Males express the characteristic of this allele even if it is recessive.

Can males be carriers of X-linked genes?

No, males cannot be carriers of X-linked genes.

What happens when a carrier female and affected male have children in terms of colour blindness probability?

There is a 50% chance of producing a child with colour blindness.

What is autosomal linkage?

Genes on autosomes that can be inherited together.

How does the proximity of genes on a chromosome affect inheritance?

Genes found close together are more likely to be inherited together.

What evidence is there for crossing over during meiosis?

The presence of recombinant gametes with linked genes.

What ratio is expected from unlinked genes during dihybrid crosses?

9:3:3:1.

How does crossing over affect alleles on the same chromosome?

It can put new alleles together in combination.

What are alleles?

Alternative forms of a particular gene with different base sequences.

What does co-dominant mean?

Alleles that both contribute to the phenotype in the heterozygous condition.

What is a dominant allele?

An allele that expresses itself in the phenotype in heterozygous organisms.

What is a gene?

A section of DNA on a chromosome that controls a feature by coding for specific polypeptides or functional RNA.

What is a genotype?

The combination of alleles present within the cells of an organism.

What does heterozygous mean?

An organism with paired alleles that are different.

What does homozygous mean?

An organism with paired alleles that are the same.

What are homologous chromosomes?

A pair of chromosomes, one from each parent, that have the same gene loci.

What is the locus?

The specific linear position of a gene on a chromosome.

What is monohybrid inheritance?

Inheritance of a single pair of alleles.

What is a phenotype?

The observable or biochemical characteristics of an organism resulting from its genotype and environmental effects.

What is a recessive allele?

An allele that does not express itself in the phenotype in heterozygous organisms.

What is the expected phenotypic ratio when two homozygous parents are crossed?

100% heterozygous offspring with the same phenotype.

What is the phenotypic ratio of offspring from two heterozygous parents (Gg)?

A 3:1 ratio of phenotypes, e.g., green:yellow pods.

What does co-dominance imply in genetics?

Both alleles are expressed in the phenotype as neither is recessive.

What factors can cause discrepancies between expected and actual offspring ratios?

Random fertilization, co-dominance, sex-linkage, and small population samples.

What causes genetic variation in gametes during meiosis?

Crossing over between chromatids and independent assortment of chromosomes.

Why are humans diploid organisms?

Because they have two copies of each chromosome (one from each parent) which means there are two alleles for each gene

What does F₁ mean

The first set of offspring of two parents