Genetics Chapter 9 and 12 Gregor Mendel

Genetics Chapter 9 and 12

Gregor Mendel ¡ ¡ ¡ 1842 Studied hereditythe transmission of characteristics from parents to offspring. Studied garden peas- Pisum sativum

Mendel's Work ¡ Looked at peas’ traits l l l Height (tall or short) flower position (axial or terminal) pod appearance (inflated or constricted) pod color (green or yellow) seed texture (smooth or wrinkled) Flower color (purple or white)

Mendel’s Methods ¡ Pollination - from anther to stigma l l Self-pollination Cross-pollination

Types of Pollination

His experiments Mated pure plants through self pollination. ¡ Created strains of plants. ¡ Created P 1 or parent generations. ¡ Crossed the plants to get F 1 or first filial generations. AKA 1 st offspring. ¡ Then crossed F 1 plants to create F 2 Plants. AKA 2 nd generation offspring. ¡

Conclusions (pg 167 -168) Axial + terminal = axial ¡ Green + yellow = green ¡ Purple + white = purple ¡ THEREFORE…. ¡ Found factors – pairs for each trait. ¡ 2 Alleles per trait (ex Gg) ¡

Recessive vs Dominant Traits Dominant = controlling or over powering allele. ¡ Recessive= overpowered not controlling allele. Can be masked ¡ Law of segregation= pair of factors is segregated, or separated, during the formation of gametes. ¡ l AKA one from dad, one from mom -> join to make a pair.

Chromosomes and Genes Molecular genetics= study of structure and function of genes. ¡ Alleles- one half of a pair of genes ¡ l ¡ ex. Aa, “A” is an allele. “a” is an allele. Probability- the likelihood that a specific event or trait will occur. l ratios

Genotype and Phenotypes Genotype= genetic makeup of an organism. (Gg) ¡ Phenotype= Physical appearance of organism as a result of its genotype. (green) ¡ Homozygous= both alleles are the same (GG) ¡ Heterozygous= alleles are different (Gg) ¡

Punnett Squares and Crosses ¡ ¡ Monohybrid Crosses- cross for ONE pair on contrasting traits. Homozygous Dominant (PP) x Homozygous Recessive (pp) B BB BB BB

Monohybrid Cont. ¡ Homozygous (BB) x heterozygous (Bb) B BB Bb Heterozygous (Bb) x heterozygous (Bb) B b B BB Bb bb b B ¡

Test Crosses ¡ ¡ Unknown genotypes of parents Known phenotypes of offspring BB=black, Bb= black, bb=brown l l 2 black: 2 brown One parent is brown (bb) ? ? b Bb bb

Incomplete Dominance ¡ ¡ ¡ Two or more alleles influence the phenotype. AKA “mixing” Neither allele is dominant EX: RR=red, Rr=pink, rr=white Geno=1 RR: 2 Rr: 1 rr Pheno=1 red: 2 pink: 1 white R r R RR (red) Rr (pink) r Rr rr (pink) (white )

Co dominance Page 176 ¡ ¡ Both alleles are expressed in heterozygous offspring. Example- a horse has a gene for both red and white hair. Therefore he has strands of white hair and strands of red hair.

Dihybrid Crosses Involves two pairs of contracting traits. ¡ EX= seed texture and seed color ¡ l l Homo Dom x Homo Recessive R (round) is dominant over r (wrinkled) Y (yellow) is dominant over y (green) Cross rryy (homogenous wrinkled green) with RRYY (homogenous round, yellow)

RRYY X rryy (Homozygous dominant X recessive) ry ry RY Rr. Yy Rr. Yy

Heterozygous X Heterozygous Rr. Yy X Rr. Yy RY Ry r. Y ry RY RRYy Rr. YY Rr. Yy Ry RRYy RRyy Rr. Yy Rryy r. Y Rr. Yy rr. YY rr. Yy ry Rr. Yy Rryy rr. Yy rryy

Hetero X Hetero Results ¡ Genotypic ratio l ¡ 1 RRYY: 2 RRYy: 2 Rr. YY: 4 Rr. Yy: 1 RRyy: 2 Rryy: 1 rr. YY: 2 rr. Yy: 1 rryy Phenotypic Ratio l l l Always 9: 3: 3: 1 (total 16) 9 dominant for both traits 1 recessive for both traits

Results Continued 9/16 ¡ 3/16 ¡ 1/16 ¡ ¡ round and yellow round and green wrinkled and yellow wrinkled and green **Remember** l 9: 3: 3: 1

Sex determination of Offspring ¡ ¡ ¡ Cross XX (mom) with XY (dad) Geno Always = 2 XX: 2 XY Pheno Always= 2 females: 2 males X XX XX Y XY XY

Sex Linkage ¡ Genes that are found only on the “X” chromosome or the “Y” chromosome. l l ¡ color blindness (inherited from mom) hemophilia Ex Fly eye color (Morgan) l l F 1= all red eyes F 2= 3 red: 1 white ¡ White was ALWAYS male ¡ THUS, eye color is carried on the “X” chromosome.

Results X Y r ¡ F 1 - all red eye because they all carry “R” ¡ F 2 - XR XRX r XRY XR XRXr XRY XR XRXR XRY l Xr XRXr Xr Y l 3 red eyed (carry “R” 1 white (does not carry “R” )

X- Influenced ¡ ¡ Traits influenced by sex hormones. Phenotypes differ even is genotypes are the same. l l l Pattern baldness B=bald B’=non bald Dominant in males, Recessive in females **Females only show if both alleles are dominant. ** XB XB’ XB XBXB (Bald because both BB) XBXB’ (not bald) YB’ XBYB’ (Bald) XB’YB’ (Bald)

Blood Type ¡ Controlled by multiple alleles l i. A, i. B, and i (i. O). l A and B are co dominant. l A and B are dominant to O. Genotype Phenotype IAIA A Ia. I A IBIB B IBI B IAIB AB II O

Pedigrees (see page 227) Record of how a trait is inherited over several generation. ¡ Determines carriers- organisms that have the gene but do not show the phenotypic trait. ¡ Used to determine genetic disorders. ¡

Additional Info Chromosome Map- diagram that shows a linear sequence of genes on a chromosome. ¡ Mutation- some sort of change in the gene sequence. Can be good or bad. ¡

Chromosome Map

Trisomy 21

Great Apes Karyotype

Mutations Cont. ¡ Chromosome Mutations l l l Deletion- loss of part of a chromosome. Inversion- break off and reattach in reverse. Translocation- break off and attaches to another chromosome.

Gene Mutations ¡ Point Mutation- substitution, addition, or removal of a single nucleotide. l Ex sickle cell anemia (A for T) Substitution- nucleotides switch ¡ Frame Shift- caused by deletion or addition. ¡

Ways to detect genetic Disorders. Genetic Screening ¡ Genetic Counseling ¡ Amniocentesis ¡ Chorionic villi sampling ¡ Pedigrees ¡

Genetic Traits and Disorders Huntington’s Disease- (single allele) ¡ Blood Type- (multiple alleles) ¡ Skin Color- (polygenic alleles) ¡ Non-disjunction (addition or subtraction of chromosomes) ¡ l l Monosomy- One chromosome Trisomy- Three chromosomes ¡ Trisomy-21 – Down Syndrome

Huntington’s Disease