1 G ENETICS Mendel’s Laws of Heredity

2 Mendel’s Laws Law of segregation The two alleles for ___________________________________ A parent will pass down ______________, only one allele for each trait Law of independent assortment Genes for ___________________________________ ___________________________________

3 Some Needed Vocabulary Heredity Passing on of characteristics ___________________________ Traits Characteristics that _________________ Genetics The study of Heredity Gametes Sex cells Sperm = male gamete Egg = female gamete

4 Gregor Mendel A monk who studied heredity using garden pea plants Why garden peas? ____________________________________________________________ What did he do? He transferred pollen from one plant ______________________________________ This is called “_________________________” Mendel first “crossed” tall plants with short plants

5 Mendel’s Monohybrid crosses Monohybrid cross Focuses on one (___________) trait 1 st generation Crossed a ___________pea plant with a ________pea plant All of the offspring were ____________ 2 nd generation Crossing the offspring of the 1 st generation _____of the offspring were tall; ______of the offspring were short _______ ratio (tall to short)

6 Mendel’s Findings Mendel found that each chromosome has two factors for each traits… called ________ Alleles = forms of genes Types of alleles (mask means hidden) Dominant The trait that has the ability to _________the other Represented with a ____________ letter (A) Recessive The trait that will be masked by the dominant trait… it will be there, but will not be show (expressed) Represented with a _______________ letter (a)

7 Phenotype vs. Genotype Phenotype The way that a___________________; how the trait appears Tall, short Genotype The offspring’s ____________________ TT, Tt, tt

8 Homozygous vs. Heterozygous _______________ (“homo” means “same”) Having two identical alleles for a trait TT, tt ________________ (“hetero” means “different”) Having two different alleles for a trait Tt

9 ____________ square Short way to find the expected proportions of possible genotypes in the offspring of a ________________.

10 Mendel’s Punnett Square 1 st generation T = Tall t = short TT x tt TT t t TtTt TtTt

11 Interpreting the Punnett Square All ____________ are heterozygous tall (Tt) Ratio ________ (Tall : Short) Percentage ________ Tall Each offspring box represents _______ of the population of offspring produced TT t t TtTt TtTt Tall = T Short = t

12 Mendel’s Punnett Square 2 nd generation Tall = ____ Short = ___ Parents: _______ x _______ oHomozygous Tall: oGenotype: _______ oHow many? ______ oHeterozygous Tall: oGenotype: _______ oHow many? ______ oShort: oGenotype: _______ oHow many? ______ oTOTAL # OF TALL: _____ oTOTAL # OF SHORT: _____ oRatio of Tall : Short  __________ oPercentages: oPercent Tall: ___________ oPercent Short: __________ T t TtTt T t T t TTTt Tttt 1 Tt 1 1 3:1 75%

13 G ENETICS Patterns of Heredity

14 Simple Mendelian Inheritance The type of inheritance we have discussed thus far (Mendel’s peas) Not all patterns in heredity are as simple… There is more than just dominant and recessive

15 Incomplete Dominance The phenotype of the ____________is intermediate (____________) between those of the two __________________. For Example: A cross between a particular RED flower and a WHITE flower will produce a _____________ flower

16 Punnett Square for Incomplete Dominance RR = Red R’R’ = White RR’ = Pink Cross: (RR) Red flower X (R’R’) White flower RR R’ R’ RR’RR’ R R’RR’

17___________________ The phenotypes of both homozygotes is produced (__________or strips) in the ________________ individual For Example: A black rooster and a white hen might produce a chick with some black feathers and some white feathers

18 Multiple Alleles Traits controlled by more than ___alleles … For Example: ______________alleles are commonly seen in the coat color of rabbits (as well as in dogs, cats, horses, humans, hamsters etc.) Also… Blood Typing…

19 Multiple Alleles – Blood Types Human blood types are determined by the ____________ or __________of certain molecules on the surfaces of red blood cells There are three alleles for blood type… I A …………………… written as “A” I B …………………… written as “B” i …………………… written as “O”

20 Sex-linked traits Traits that are controlled by genes located on sex chromosomes These traits help explain why some characteristics and disorders are more common in one sex than in the other Commonly referred to as “X-linked” because the trait is usually linked to the X- chromosome

21 Background Information Humans have _______chromosomes; or ________ pairs of chromosomes Of these, 22 pairs are autosomes auto means “self” (“self” chromosomes for the body) The last (23 rd ) pair is different in males & females… these are the ______ chromosomes Females have two “X” chromosomes (______) Males have one “X” and one “Y” chromosome (_____)

22 “Sex-linked” traits B = Blue eyes b = Green eyes Green-eyed male (X b Y) X Heterozygous Blue-eyed female (X B X b ) X __ Y XBXbXBXbXBXbXBXb XbXbXbXbXbXbXbXb XbYXbYXbYXbY XBYXBYXBYXBY

23 “Sex-linked” traits B = Blue eyes b = Green eyes Green-eyed male (X b Y) X Heterozygous Blue- eyed female (X B X b ) XbXbXbXb Y XBXBXBXB XbXbXbXb XBXbXBXbXBXbXBXb XbXbXbXbXbXbXbXb XbYXbYXbYXbY XBYXBYXBYXBY OFFSPRING MALES (XY) MALES (XY) Blue EyesBlue Eyes Genotype _______Genotype _______ How many? _____How many? _____ Green EyesGreen Eyes Genotype _______Genotype _______ How many? _____How many? _____ FEMALES (XX)FEMALES (XX) Blue EyesBlue Eyes Genotype _______Genotype _______ How many? _____How many? _____ Green EyesGreen Eyes Genotype _______Genotype _______ How many? _____How many? _____ XBYXBY XbYXbY 1 1 XBXbXBXb 1 XbXbXbXb 1

24 MalesFemales Sex-linked percentages B = Blue eyes b = Green eyes Green-eyed male (X b Y) X Heterozygous Blue- eyed female (X B X b ) XbXbXbXb Y XBXBXBXB XbXbXbXb XBXbXBXbXBXbXBXb XbYXbYXbYXbY oPercentages oWhen figuring percents for sex-linked punnett squares, you must be careful to only count what is asked for…  % of females with blue eyes  % of males with blue eyes  % of females with green eyes  % of males with green eyes 50% 50% 50% 50%

25 Polygenic Inheritance When a trait is controlled by more than one gene For Example: Skin color is actually the accumulation of dominant genes for pigment in the skin