Explanation

Explanation

Thomas Hunt Morgan was awarded the 1933 Nobel Prize

In Physiology or Medicine

Awarded Nobel Prize for heredity transmission functions of chromosomes.

He showed that genes are linked in a series of chromosomes and are responsible for identifiable, hereditary traits.

Morgan's work played a key role in establishing the field of genetics

Explanation

Metaphase, one of the most critical stages in mitosis

Chromosomes are most compact in metaphase

When the centromeres of the chromosomes of all cells are aligned with the equator of the mitotic spindle.

Chromosomes are most easily visualized at this stage,

So metaphase is especially useful in cytogenetics.

Explanation

Hardy-Weinberg's principle states that "gene frequency in a population remains stable and constant from generation to generation".

Hardy and Weinberg used mathematics to describe:

Equilibrium population (p = frequency of A, q = frequency of a, so p + q = 1)

p2 + 2pq + q2 = 1.

Where p and q are frequency of the dominant and recessive allele respectively.

This equation can also be used to calculate the genotypic frequencies in a population at equilibrium.

p2= homozygous dominant frequency

q2= homozygous recessive frequency

2pq= heterozygous frequency

Explanation

The French scientist Georges Cuvier popularised the concept of catastrophism in the early 19th century

He proposed that

" new life forms had moved in from other areas after local floods, and avoided religious or metaphysical speculation in his scientific writings".

Explanation

In organisms such as grasshoppers, crickets, and other insects

The female sex is heterogametic i.e. XX.

The male sex is homogametic i.e. XO.

In males, the gametes produced have an X chromosome and the other gamete is without any chromosome O.

This is an XX-XO sex-determination system in grasshoppers.

Explanation

Human placental lactogen and leutotrophic is a hormone responsible for lactation

Human placental lactogen (hPL) is a hormone released by the placenta during pregnancy.

Leutotrophic hormone stimulates the growth of the milk gland and secures milk only after delivery of the fetus plus the placenta. 

It gives nutrition to the fetus.

It also stimulates milk glands in the breasts for breastfeeding.

Additional information:

Lactation is the process of producing and releasing milk from the mammary glands in your breasts.

It begins in pregnancy when hormonal changes signal the mammary glands to make milk in preparation for the birth of your baby.

Explanation

In honey bees, sex determination is based on the number of chromosomes an individual receives.

By parthenogenesis, an offspring created by the combination of a sperm and an egg develops as a female (queen or worker)

while an unfertilized egg develops as a male (drone).

Explanation

Smooth muscles are not striated

Because their cells are arranged in sheets instead of bundles.

They do not have organized sarcomeres.

Additional information:

Both skeletal and cardiac muscles appear striated, or striped,

Because their cells are arranged in bundles

However skeletal muscle fibers are multinucleated.

Whereas, the cardiac muscle fiber is uninucleated.

Explanation

Nissl bodies are composed of rough endoplasmic reticulum (RER) and free ribosomes.

It is also called a nissl substance.

It is a large granular body present in neurons.

Their main function is to synthesize and release proteins that are important for neuronal growth and regeneration of axons.