Patterns and Processes in Inheritance

Question 1

What is selective breeding? Give an example.

Answer 1

Selective Breeding - choosing and breeding specific plants and animals for particular physicals

For example: to develop, gradually hundreds of breeds of dogs with specific attributes.

Question 2

Briefly describe two early explanations of inheritance.

Answer 2

• Egg and sperm consist of particles, called pongees, from all parts of the body. Upon fertilization of the egg by a sperm, the pen genes develop into the parts of the body from chi they were derived. The theory of pangenesis was accepted for hundred of years, but there was no experiment for results.
• The idea of bleeding was become popular during the 1800s. The scientist believe the working theory of inteheritance. Scientists believed that characteristics of the parents blended in the offspring in a way that was irreversible; scientists believed that the original parental characteristics would not reappear in future generation.

Question 3

Explain how a hybrid plant is different from a true breeding plant.

Answer 3

A hybrid plant - the offspring of a cross between two parents organisms with different inheritable traits.

True Breeding - plants exhibits the same characteristics generation after generations.

Question 4

Explain the difference between P, F1, and F2 generations in a cross.

Answer 4

P is the true breeding plants - the parental, or P, generation.

He started his experiments by crossing true breeding plants for each characteristic with true breeding plants having the opposite characteristics.

• F1 is the filial “the first offspring”
• F2 is “the second offspring”

The F1 and F2 self- pollinate and then observed the characteristics of their offspring,

F1 and F2 plants and counted how many plants produced which characteristics.

Question 5

State Mendel’s first law in your own words, and use an example.

Answer 5

All individuals have two copies of each factor. During the copies segregate

( separate) randomly during gamete formation, and each gamete receives one copy of every factor.

For example: F1 = a nice pod shape vs F2 = a pinched pod shape

Question 6

State the meanings of the terms dominant and recessive

Answer 6

Dominant allele uses the First Letter to description of the dominance.

Recessive Allele uses the lower case to represent the recessive.

Question 7

Distinguish between the terms gene and allele.

Answer 7

Allele - different form of the same gene

Gene - unit of DNA instructions located on chromosomes coding for specific traits.

Question 8

Distinguish, using an example between the term genotype and phenotype.

Answer 8

Genotype - indicates the alleles that the organism has inherited regarding a particular trait

Phenotype - the actual visible trait of the organism.

For example:

Genotype = outward expression of the trait;

phenotype = physical form that you can observe.

Question 9

What does it mean to be homozygous for a trait? How is this different from being heterozygous?

Answer 9

Homozygous - An individual with two identical alleles for a trait

For example: RR or rr

Heterozygous - An individual with two different alleles for trait

For example: Rr

Question 10

What is a Punnett square?

Answer 10

A technique applied to the F1 cross by analyzing the genotypes to determines the phenotypes

Question 11

What is a test cross?

Answer 11

A test cross is a cross between the organism of unknown genotype and homozygous recessive organism

Question 12

State Mendel’s second law in your own words

Answer 12

The two alleles for one gene segregate (assort) independently of the alleles for other genes during gamete formation.

Question 13

Explain what incomplete dominance is.

Answer 13

Incomplete Dominance - describes a condition in which neither of two alleles for the same gene can completely conceal the presence of the other,

Question 14

Give two example of genetic conditions in humans that exhibit incomplete dominance, and briefly describe what they are.

Answer 14

1. Sickle cell anemia-one of a group of inherited disorders known as sickle cell disease. It affects the shape of red blood cells, which carry oxygen to all parts of the body.
2. Familial hypercholesterolemia - Familial hypercholesterolemia is a disorder that is passed down through families. It causes LDL (bad) cholesterol level to be very high. The condition begins at birth and can cause heart attacks at an early age.

Question 15

Explain how co-dominance is different from incomplete dominance.

Answer 15

Co-dominance is a situation in which both alleles are fully expressed.

Incomplete dominance - describe a condition in which neither of two alleles for the same gene can completely conceal the presence of the other.

Question 16

Explain why the roan colouring of a horse is an example of co-dominance.

Answer 16

A roan animal is a heterozygote in which both the base colour and white are fully expressed.

Question 17

Give two example of how the moment of alleles is consistent with the movement of chromosomes during meiosis.

Answer 17

1. the patterns for two alleles of the gene, according to Mendel’s Law of segregation.
2. Genes come in pairs, as do chromosomes; during gamete formation, alleles segregate just as homologous chromosomes.

Question 18

Differentiate between the chromosomes theory of inheritance and the gene chromosomes theory.

Answer 18

The chromosomes theory of inheritance - genes are carried on chromosomes, and chromosomes segregate independently into gametes during meiosis.

The gene-chromosome theory - that genes exist at specific arranged in a linear manner along chromosomes.

Question 19

What is chromosomes mapping?

Answer 19

The concept of crossing over is used to determine the relative positions of genes on a chromosomes in a process

Question 20

What is a map unit?

Answer 20

Defined as the distance between points on a chromosomes where a crossover is likely to occur in 1% of all meiotic events.

Question 21

Distinguish between the terms recombinant types and parental types.

Answer 21

Recombinant types -different combination of alleles, than the chromosomes of the P generation

Parental types = their chromosomes are identical to those of the P generation.

Question 22

What are sex-linked traits?

Answer 22

Traits that are controlled by genes on either the X or Y chromosomes

Punnett squares can be used to predict the outcomes of crosses that involves sex- linked traits.

Question 23

Explain why the formation of a Barr body mean that human female have only functioning X chromosomes in each somatic cell.

Answer 23

One of X is inactive and condensed tightly into a structure, which is why X chromosomes forms a Barr body random

Question 24

Explain how the formation of a Barr body counts for the coat colour of a tortoiseshell cat.

Answer 24

Because females have two X chromosomes, they have two sets of genetic information that can determine their coat color. The embryo shuts off one X chromosome in each cell, resulting in orange and black color variations in their coats.

Question 25

What are multiple alleles?

Answer 25

Most other organisms, many genes have more than two alleles.

A gene with more two alleles.

Question 26

What is the difference between a trait that has multiple alleles and a trait that is controlled by multiple genes? Give an example of each.

Answer 26

• Any individual organisms has only two alleles for each gene ( one alleles on each homologous, but many different alleles exist within the population as a whole.

For example: Gene that controls soar colour in rabbits.

• A group of genes that all contribute to the same trait is a polygene. Each dominant allele contributes to the trait.

For example: adds tp the person’s height, but recessive alleles do not contribute to the trait.

Question 27

What is a continuous trait?

Answer 27

continuous traits - traits for which the phenotypes vary gradually from one extreme to another

For example: height in humans, ear length in corn, kernel ocular in wheat, and weight of beans

Question 28

Given an example of one way (other than the ways described above) that environment can influence the expression of genetic traits.

Answer 28

An example,

Some genes are influences by temperature like the colour pattern of Himalayan rabbits. The colour is similar to the pattern of Siamese cats. Their few is pigmented on the cooler parts of their bodies; the face, ears, tails, and feet. Some animals, dark colour is the result of a gene that is only active below a certain temperature

The effect of a gene influenced by temperature can be seen in fruit flies. The expression of a mutant form called curly wings depends on the temperature. If flies that are homozygous for the curly wings are raised at 25C, their wing for curly wings, but if they raised at 16C, their wings will be straight.

Question 29

Give an example of how selective breeding has developed a new species of plant or animal.

Answer 29

An example, is rapeseed oil which was banned because erucic acid and glucosinolates are are toxic to laboratory animals. It was banned for human consumption. In 1970s, they developed canola oil which is less erucic and glucosinolates that approved for human consumption.

Question 30

Distinguish between the meaning of Roman numerals and arabic numeral in a pedigree.

Answer 30

All pedigree charts use certain conventions. Arabic numerals identify individuals, and Roman numerals identify members of the same generation that are displayed in a horizontal row. Squares represent males, and circles represent females.

Question 31

What is autosomal inheritance?

Answer 31

All pedigree charts use certain conventions. Arabic numerals identify individuals, and Roman numerals identify members of the same generation that are displayed in a horizontal row. Squares represent males, and circles represent females.

Question 32

How did pedigrees for autosomal recessive and X-linked recessive traits differ?

Answer 32

• In X-linked recessive traits, males are much more commonly affected than females. In autosomal traits, both males and females are equally likely to be affected (usually in equal proportions).
• In autosomal recessive pedigrees tend to show fewer affected individuals and are often described as “skipping” generations. Thus, the major feature that distinguishes autosomal recessive from dominantly inherited traits is that unaffected individuals can have affected offspring.

Question 33

Can a female hemophilia? Explain.

Answer 33

The male are at a much greater risk of being affected by hemophilia than females. It also shows that woman who do not have the condition can pass on the trait to their children. From this information, you can deduce that hemophilia is an X-linked recessive trait.