Bio- Modern Genetics

What is the secret of life according to the lecture notes?

The sequence of bases in DNA that code for the sequences of amino acids in proteins.

What did Walter Sutton propose in the Chromosome Theory?

Genes are located on chromosomes, each occupying a specific place called the locus.

What is the principle of segregation in genetics?

Pairs of chromosomes separate when gametes form.

What are linked genes?

Genes that are inherited together because they are on the same chromosome and do not undergo independent assortment.

What model organism did Thomas Hunt Morgan use for genetic studies?

Fruit flies.

In Morgan's experiments, what phenotype was expected in the F1 generation from the cross of gray normal wings and black small wing flies?

All flies had gray bodies with normal wings.

What did Morgan's test cross reveal about body color and wing size genes?

These traits are linked and do not assort independently.

How many linkage groups do fruit flies have?

Four linkage groups.

What is the effect of crossing over in genetics?

It produces individuals with rearranged linkage, known as recombinants.

What determines the sex of an individual in humans?

The combination of sex chromosomes, with XX for female and XY for male.

How are recessive X linked traits expressed in males?

They are more expressed in males since there is no other X chromosome that may have a dominant allele.

What was the result of the cross between a white-eyed male and a homozygous red-eyed female in Morgan's experiments?

All offspring in F1 had red eyes; the white-eyed trait appeared in F2 males only.

Define incomplete dominance with an example.

Where the active allele does not completely compensate for an inactive allele; for example, crossing red and white carnations results in pink offspring.

What is codominance in genetics?

A situation where both alleles are expressed; for example, in cattle, red x white results in roan (both colors expressed).

What type of inheritance does height represent?

Polygenic inheritance, as it is controlled by many genes and follows a gradient.

What are the possible features of type A blood?

Antigen- A, antibodies- anti-B, possible genotypes- I^AI^A or I^Ai.

What are the possible genotypes for type B blood?

I^BI^B or I^Bi.

What is unique about type AB blood?

Antigen- A and B, antibodies- neither, possible genotype- I^AI^B.

What are the features of type O blood?

Antigen- neither, antibodies- anti-A and anti-B, possible genotype- ii.

What is chromosome theory of inheritance?

The chromosome theory of inheritance states that genes are located on chromosomes, and that chromosome segregation during meiosis is responsible for the inheritance of traits.

Who proposed the chromosome theory of inheritance?

The chromosome theory of inheritance was proposed by Walter Sutton and Theodor Boveri in the early 20th century.

What are chromosomes made of?

Chromosomes are made of DNA and proteins, which together form chromatin.

How many chromosomes do humans have?

Humans typically have 46 chromosomes, arranged in 23 pairs.

What is the role of meiosis in chromosome theory?

Meiosis is the process that produces gametes with half the number of chromosomes, ensuring genetic diversity and proper chromosome number in offspring.

What is an allele?

An allele is a variant form of a gene located at a specific position on a chromosome.

What is the significance of chromosomal recombination?

Chromosomal recombination during meiosis increases genetic diversity by allowing exchange of genetic material between homologous chromosomes.

What are sex chromosomes?

Sex chromosomes determine the sex of an organism; in humans, they are X and Y chromosomes.

How do Mendel's principles relate to chromosome theory?

Mendel's principles of inheritance, including segregation and independent assortment, are explained by the behavior of chromosomes during meiosis as described by chromosome theory.

What is the principle of segregation?

Mendel's principle of segregation states that during gamete formation, the two alleles for a gene separate from each other, which is consistent with the separation of homologous chromosomes during meiosis.

What is the principle of independent assortment?

Mendel's principle of independent assortment states that genes for different traits are inherited independently of one another, which aligns with the behavior of non-homologous chromosomes during meiosis.

What did Mendel use to formulate his principles?

Mendel used pea plants to formulate his principles of inheritance, observing the inheritance patterns of traits.

What is the significance of Mendel's work in genetics?

Mendel's work laid the foundation for modern genetics, providing the first clear explanation of how traits are inherited, which is later integrated into the chromosome theory of inheritance.

How did chromosome theory advance Mendelian genetics?

Chromosome theory provided a scientific basis for Mendelian genetics by connecting the observed patterns of inheritance to the physical mechanisms of chromosome behavior during meiosis and fertilization.

What role do genes play in Mendel's principles and chromosome theory?

In both Mendel's principles and chromosome theory, genes are the units of inheritance that occupy specific locations (loci) on chromosomes, influencing the traits of an organism.

What is codominance?

Codominance is a genetic phenomenon in which both alleles in a heterozygote are fully expressed, resulting in offspring with a phenotype that is neither dominant nor recessive.

Example of codominance

An example of codominance is the AB blood type in humans, where both A and B alleles are equally expressed.

What is incomplete dominance?

Incomplete dominance is a genetic condition in which a heterozygote expresses a phenotype that is intermediate between the phenotypes of the two homozygotes.

Example of incomplete dominance

An example of incomplete dominance is the flower color in snapdragons, where red and white flowers produce pink offspring.