Genetics 2

1. Lecture Notes Genetics 2

2. Sometimes traits appear to combine or mix. Think about the mixing of colors- Yellow and Blue make Green Alleles can mix in a similar way. This is called= Mendel’s experiments lead to the idea of dominant and recessive genes.

3. Incomplete Dominance - One allele is notcompletely dominant over another. -Incomplete Dominance is a situation where two or more alleles influence the phenotype, which is in between that of the parents. Incomplete Dominance

4. Example – Red and white flowers are crossed and pink flowers are produced. • RR=Red • WW=White • RW=Pink R R W W

5. Example – straight, wavy, or curly hair • Cross a straight hair individual with a curly hair individual. • Straight hair= SS • Curly hair= CC • Wavy hair= SC

6. Co-dominance - Both alleles of a gene contribute to the phenotype of the organism. Co-dominance

7. Example – A solid white cow is crossed with a solid brown cow and the resulting offspring are spotted brown and white (called roan). • + Co-dominance

8. Example – brown cow (RR) crossed with a white cow (R’R’) • Brown= RR • White= R’R’ • Roan= RR’ • Notice all of the offspring are Roan (RR’) R R R’ R’

9. Multiple Alleles- When genes have 3 or more alleles available in the population an individual will still only carry 2 alleles (1 from each parent). An example is ABO blood group What is blood made of? Multiple Alleles

10. HUMAN blood type

11. The Rhesus, or Rh, factor is a kind of protein found on red blood cells. An Rh factor that is either positive, meaning the factor is present, or that is negative, meaning the factor is absent,Read more: http://www.livestrong.com/article/178904-negative-blood-types-with-negative-rh-factors/#ixzz15aCKsWBn

12. 4 types of HUMAN blood Blood type chart go to web page below Phenotype (Blood Type Safe Transfusions Genotype Antigen on Red Blood Cell From To http://nobelprize.org/educational/medicine/landsteiner/readmore.html

13. The Rhesus system is the second most significant blood group system in human blood transfusion. The most significant Rhesus antigen is the RhD antigen because it is the most immunogenic of the five main rhesus antigens.

14. CC, Ccch, Cch or Cc Full color; dominant to all alleles cchc, cchcch, cchch Chinchilla color; partial defect in pigmentation chc or chch Himilayan color; color in certain parts of body cc Albino; no color Example - Coat color in rabbits is determined by a single gene that has at least four different alleles. Different combinations of alleles result in the four colors you see

15. Polygenic Trait - Trait controlled by two or more genes. • Polygenic traits often show a wide range of phenotypes. • Example: eye and skin color is determined by distribution of pigment and tone amount. Pleiotrophy – a condition where one pair of genes influences several triats Polygenic Trait

16. Sex Chromosomes- X and Y Egg cells are all X Sperm cells can be either X or Y A Sex Chromosome carries the gene that determines an individual’s sex. XX-Female XY-Male

17. Some traits are controlled by alleles located on sex chromosomes. Sex-linked Genes – genes found only on either the X or Y chromosome. Sex-linked genes

18. Traits whose alleles are located only on the X chromosome are said to be X-Linked traits. • Example- hemophilia (absence of normal clotting factor in blood) is x-linked recessive.

19. Example – red/green color blindness is x-linked recessive. Father- (Normal Vision) Color Normal Blind Male Female Mother (Carrier)

20. Sex-limited traits • only expressed in the presence of sex hormones • observed in one sex or the other • Typically do not appear until puberty when sex hormones are produced • Example – beards in men • Example – milk production in females Sex-limited traits

21. Pedigree – a chart that shows a trait and how it is inherited within a family • Helps to predict certain alleles and traits in offspring • Helps to trace the origin of the trait Pedigrees

22. Pedigrees I, II, III… Generations 1, 2, 3, … Individuals

23. What is the gender of person II-3? • Is III-2 afflicted with this trait? • How many children are in generation III? • What is the genotype of: • II-1? • II-2? Sample Pedigree #1 This pedigree is for an autosomal recessive trait.

24. Design a pedigree for an autosomal recessive trait, blue eyes, from the following family history. Sample Pedigree #2 Grandma had blue eyes, but grandpa did not. They had 3 children: Jermaine, Michael, and Janet. Jermaine has blue eyes, but Michael and Janet do not. Janet married Justin and their 2 sons both had blue eyes.

25. A photograph of all of an organism’s chromosomes. • This allows scientists to study differences in size, shape, and structure of chromosomes. • Chromosomal abnormalities can then be observed • Chromosomes are arranged by size. Karyotypes

26. The 23rd pair of chromosomes is always the sex chromosomes Chromosomes that do not identify the sex of an organism are called autosomes. Karyotype - Human

27. Nondisjunction – the failure of a homologous chromosome to separate during cell division (meiosis) resulting in abnormal number of chromosomes in gametes, thus leading to abnormal amount in the zygote. • 3 types • Monosomy • Trisomy • Polyploidy Chromosomal mutations

28. The zygote (fertilized egg) has only one copy of a chromosome. Monosomy Missing Chromosome

29. Example – Turner’s Syndrome is monosomy of the sex chromosome (XO); results in a sterile female whose sex organs will not develop until puberty Monosomy

30. The zygote has 3 copies of a chromosome. trisomy

31. EX: Down’s Syndrome: trisomy of chromosome #21 trisomy Symptoms can include: -mental retardation -enlarged tongue and palate malformation -weakened muscles -short stature -heart defects

32. EX: Klinefelter’s Syndrome: trisomy of sex chromosomes (XXY) trisomy

33. Nondisjunction occurs in all chromosomes so a complete set of chromosomes fails to separate during meiosis leading to many extra copies of chromosomes • Example – rarely seen in animals • Example – may result in hardier, healthier, larger plants polyploidy Karyotype of Wheat