HEREDITY and VARIATION. Part II: Non-Mendelian Patterns of Inheritance

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1 HEREDITY and VARIATION Part II: Non-Mendelian Patterns of Inheritance

2 Human traits are inherited in different patterns of inheritance. Has progressed over the last decade after the completion of the HUMAN GENOME PROJECT (HGP) in The project aimed to identify the genes associated with genetic disorders. Ways of inheriting traits: a) Traits controlled by a single gene but with two contrasting alleles b) Traits controlled by a single gene with multiple alleles c) Traits controlled by several genes interacting to one another

3 Non-Mendelian Patterns of Inheritance Refers any pattern of inheritance in which traits do not segregate in accordance with Mendel s laws. Incomplete dominance Codominance Sex determination Sex-linked traits

4 Traits controlled by a single gene but with two contrasting alleles, one dominant & one recessive. HUMAN TRAITS DOMINANT ALLELES RECESSIVE ALLELES SHAPE OF EARLOBE FREE EARLOBE ATTACHED EARLOBE HAIR PATTERN ON FOREHEAD WIDOW S PEAK STRAIGHT PATTERN HAIR TEXTURE STRAIGHT HAIR CURLY HAIR ABILITY TO ROLL THE TONGUE TONGUE ROLLERS NON-TONGUE ROLLERS

5 Incomplete Dominance is a situation in which one allele is not completely dominant over another. Example Red and white flowers are crossed and pink flowers are produced.

6 CODOMINANCE is a situation in which both alleles of a gene contribute to the phenotype of the organism. + Example A solid white cow is crossed with a solid brown cow and the resulting offspring are spotted brown and white (called roan).

7 POLYGENIC TRAIT is a trait controlled by two or more genes. * Shows a wide range of phenotypes. Example The wide range of skin color in humans comes about partly because more than four different genes probably control this trait.

8 MULTIPLE ALLELES is a situation having three or more alleles of the same gene. Note: Even though three of more alleles exist for a particular trait, an individual can only have two alleles one from the mother and one from the father.

9 MULTIPLE ALLELES is a situation having three or more alleles of the same gene. Hair color: Too many alleles exist to count. There are over 20 different shades of hair color.

10 MULTIPLE ALLELES is a situation having three or more alleles of the same gene. Blood type: Three (3) alleles exist (I A, I B, and i), which results in four different possible blood types.

11 Sex-Linked disorders are any disease or abnormality that is determined by the sex hormones. Lesch-Nyhan Syndrome a rare hereditary disease that affects young boys, usually causing early death. It is marked by compulsive self-mutilation of the head and hands, together with mental retardation and involuntary muscular movements.

12 COLOR-BLINDNESS an inability to distinguish between red and green and sometimes between blue and yellow, is caused by a defect in one of the three color-sensitive cells in the retina Color blindness affects approximately one person in thirty

13 COLOR-BLINDNESS DESCRIPTION GENOTYPE Pedigree SYMBOL FEMALE X C X C CARRIER FEMALE X C X c? AFFLICTED FEMALE NORMAL MALE AFFLICTED MALE X c X c X C Y X c Y

14 COLOR-BLINDNESS 1. A woman is color blind. What are the chances that her sons will be color blind? If she is married to a man with normal vision, what are the chances that her daughter will be color blind? Will be carriers? 2. Red-green color-blindness is caused by an X-linked recessive allele. A color blind man marries a woman with normal vision but whose father is color-blind. Will they have a color blind daughter? Color blind son? Why or why not? Construct a chart showing the pedigree of this family.

15 HEMOPHILIA a rare bleeding disorder in which the blood doesn't clot normally.

16 HEMOPHILIA DESCRIPTION GENOTYPE SYMBOL NORMAL FEMALE X H X H? CARRIER FEMALE X H X h? AFFLICTED FEMALE X h X h? NORMAL MALE X H Y? AFFLICTED MALE X h Y?

17 TRIVIA Did you know that BALDNESS (Alopecia) is an example of a SEX- INFLUENCED trait and is inherited as a dominant allele? And the male hormone DHT (dihydrotestosterone) activates the trait.

18 Pedigree analysis and karyotyping help explain the inheritance of human traits. Pedigree = a chart that shows the family history and illustrates how a trait is inherited over several generations.

19 Another method to study inheritance is through a process called KARYOTYPING.

20 There are several practical applications of one s knowledge about chromosomes and genes. (application of genetics) PLANT BREEDING Better Crop Varieties (Conventional plant breeding) Genetically modified foods (Ex. FlvrSavr tomatoes; seedless watermelons) Food security and supply (Modern methods of farming)

21 There are several practical applications of one s knowledge about chromosomes and genes. (application of genetics) ANIMALS Improving animal breeds Polyploidy = leads to the expression of desirable traits Animal husbandry = increased milk & butterfat production, leaner meat & resistance to parasites & pathogens) Selective breeding TRANSGENIC ANIMALS Recombinant Proteins (collagen, fibrinogen, fertility hormones) Produce useful organs (pigs that manufacture liver for human liver transplants) Study the effects of drugs and how diseases develop

22 The following are cloned animals used for different purposes. MIRA & her sisters- To contain pharmaceutical products for humans (1998) (Millie, Alexis, Christa, Dotcom, Carrel) reproduce human organs (2000) ANDI use for laboratory Experiments (2000) CC for business reproducing pets (2001) SNUPPY study human diseases (2005)

23 References Ferriols-Pavico, et. Al. Exploring Life Through Science. Phoenix Publishing House Rabago, L. et. Al. Science and Technology. Vibal Publishing House Capco, C and Yang, G. Biology, You and the Natural World. Phoenix Publishing House Jeff Hildebrant (Writer, Producer & Director). A Film on Genetics and Heredity. Great Pacific Media Scientific American Journal. Miriam-Webster Dictionary Youtube videos Google images National Human Genome Research Institute

24 References