L5: Principles of heredity and family pedigree Flashcards
What is DNA?
What provides the key to genetic diversity among living organisms?
Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.
What is a chromosome and how many chromosomes do humans have?
What are genes?
Describe the experiment of plant hybridization done by the father of genetics Mendel
What is heredity?
Transmission of genetic information from parent to offspring
What is genetics?
The science of heredity (branch of biology that deals with heredity and variation of organisms).
What is Genome?
the entire set of genes in an organism
What is a locus?
Each gene has a specific site on a certain chromosome (fixed positions).
What are alleles or alternative forms?
The forms of the gene found at a particular locus, One allele is inherited from father and the other from mother.
What are homozygous alleles?
Both alleles of a pair are the same TT, tt
What are heterozygous alleles?
Both alleles of a pair are not the same Tt
What are dominant alleles?
the allele of a gene that masks or suppresses the expression of an alternate allele; the trait appears in the heterozygous condition.
What are recessive alleles?
an allele that is masked by a dominant allele; does not appear in the heterozygous condition, only in homozygous.
What is a trait?
Any genetically determined characteristics of the individual
What does genotype mean?
the genetic makeup of an organisms. alleles carried by anindividual eg. RR, Rr, rr. (internal information)
What does phenotype mean?
- the physical appearance of an organism (Genotype + environment) (external appearance).
- physical characteristic or appearance of an individual
Give an example that illustrates basic terms of genetics
Trait: eye colour
Genotype: BB. Bb, bb
phenotype: brown or blue
Dominant allele: B
Recessive allele: b
What are Mendel’s principles?
- Principle of Dominance
- Principle of Segregation
- Principle of Independent Assortment
Describe Mendel’s principle of dominance
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.
Describe Mendel’s principle of segregation
When gametes are formed, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene.
Describe Mendel’s principle of independent assortment
the alleles for one trait separate independently of the alleles for other traits during gamete formation
What is punnett square?
It is a chart that allows to easily determine the expected ratios of possible genotypes in the offspring of two parents.
What is the definition of a family pedigree and what is its importance?
• 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.
What are other types of inheritance that Mendel never considered?
• Incomplete Inheritance
• Codominance
• Multiple Alleles
• Polygenic Traits
• Sex-linked
What does of the heterozygous offspring in case of incomplete inheritance display?
and give an example for it
• 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.
Describe multiple alleles theory and give an example for it
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]
describe co-dominance theory and give an example for it
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
Describe polygenic inheritance and give an example for it
• 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.
Describe sex-linked genetics
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.
Remember the following notes about Sex-linked Inheritance
When will males or females show X-linked recessive disorders?
- 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
Give an example of X-linked recessive disorders
(Homozygous recessive)
* Hemophilia: Inability to have clotting of blood, XhColor blindness: Xc
