L5: Principles of heredity and family pedigree

Question 1

What is DNA?

Answer 1

Question 2

What provides the key to genetic diversity among living organisms?

Answer 2

Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.

Question 3

What is a chromosome and how many chromosomes do humans have?

Answer 3

Question 4

What are genes?

Answer 4

Question 5

Describe the experiment of plant hybridization done by the father of genetics Mendel

Answer 5

Question 6

What is heredity?

Answer 6

Transmission of genetic information from parent to offspring

Question 7

What is genetics?

Answer 7

The science of heredity (branch of biology that deals with heredity and variation of organisms).

Question 8

What is Genome?

Answer 8

the entire set of genes in an organism

Question 9

What is a locus?

Answer 9

Each gene has a specific site on a certain chromosome (fixed positions).

Question 10

What are alleles or alternative forms?

Answer 10

The forms of the gene found at a particular locus, One allele is inherited from father and the other from mother.

Question 11

What are homozygous alleles?

Answer 11

Both alleles of a pair are the same TT, tt

Question 12

What are heterozygous alleles?

Answer 12

Both alleles of a pair are not the same Tt

Question 13

What are dominant alleles?

Answer 13

the allele of a gene that masks or suppresses the expression of an alternate allele; the trait appears in the heterozygous condition.

Question 14

What are recessive alleles?

Answer 14

an allele that is masked by a dominant allele; does not appear in the heterozygous condition, only in homozygous.

Question 15

What is a trait?

Answer 15

Any genetically determined characteristics of the individual

Question 16

What does genotype mean?

Answer 16

the genetic makeup of an organisms. alleles carried by anindividual eg. RR, Rr, rr. (internal information)

Question 17

What does phenotype mean?

Answer 17

• the physical appearance of an organism (Genotype + environment) (external appearance).
• physical characteristic or appearance of an individual

Question 18

Give an example that illustrates basic terms of genetics

Answer 18

Trait: eye colour
Genotype: BB. Bb, bb
phenotype: brown or blue
Dominant allele: B
Recessive allele: b

Question 19

What are Mendel’s principles?

Answer 19

1. Principle of Dominance
2. Principle of Segregation
3. Principle of Independent Assortment

Question 20

Describe Mendel’s principle of dominance

Answer 20

One allele masked another; one allele was dominant over the other.
* Each trait is controlled by 2 factors (alleles), one factor (dominant) may mask the other factor (recessive) preventing it from having an effect.

Question 21

Describe Mendel’s principle of segregation

Answer 21

When gametes are formed, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene.

Question 22

Describe Mendel’s principle of independent assortment

Answer 22

the alleles for one trait separate independently of the alleles for other traits during gamete formation

Question 23

What is punnett square?

Answer 23

It is a chart that allows to easily determine the expected ratios of possible genotypes in the offspring of two parents.

Question 24

What is the definition of a family pedigree and what is its importance?

Answer 24

• A family pedigree shows how a trait is passed from generation to generation within a family.
• A pedigree can show\whether a Mendelian trait is autosomal or x-linked trait/ dominant or recessive.

Question 25

What are other types of inheritance that Mendel never considered?

Answer 25

• Incomplete Inheritance • Codominance • Multiple Alleles • Polygenic Traits • Sex-linked 

Question 26

What does of the heterozygous offspring in case of incomplete inheritance display?  and give an example for it

Answer 26

• The heterozygous offspring displays a THIRD Phenotype!! (intermediate in phenotype)  • A good example of incomplete dominance in humans is hair type.  • There are genes for straight and curly hair, and if an individual is heterozygous, they will typically have the phenotype of wavy hair.

Question 27

Describe multiple alleles theory and give an example for it

Answer 27

Genes often exist in several different forms and are therefore said to have multiple alleles.  Example: Human Blood group (A, B, O, or AB) Multiple allele A, B, and O, A and B dominant / O recessive,[3 alleles & 4 phenotypes]

Question 28

 describe co-dominance theory and give an example for it 

Answer 28

Both traits are dominant and show up in the phenotype together. [Co means “together”] they both influence the phenotype.  Both alleles of a gene are expressed in the phenotype. in human; AB blood group 

Question 29

Describe polygenic inheritance and give an example for it 

Answer 29

• Traits controlled by interaction of two or more genes (multiple genes) are said to be polygenic traits.  • E.g. skin color and height.  • Skin color is a common example of a polygenic trait it is governed by 6 loci and at least 12 alleles.

Question 30

Describe sex-linked genetics

Answer 30

Sex is determined by sex chromosomes X and Y  XX= female, XY = male  The X chromosome contains many important genes that are unrelated to sex determination, These genes are required for both males and females  A male receives ALL of his X-linked genes from his mother while a female receives her X-linked genes from both parents.

Question 31

Remember the following notes about Sex-linked Inheritance 

Answer 31

Question 32

When will males or females show X-linked recessive disorders?

Answer 32

*  Males will show this trait if they have the recessive allele on the X chromosome                                                                                                             *  Females will show this trait if they have the recessive allele on both X chromosomes

Question 33

Give an example of X-linked recessive disorders

Answer 33

(Homozygous recessive)  *  Hemophilia: Inability to have clotting of blood, Xh Color blindness: Xc