Gene$cs the study of heredity

Transcription

1 Gene$cs the study of heredity Based on the study of probability (likelihood) 1. Why should we study gene$cs? Disease causes/treatments Biotechnology agriculture, animal husbandry Breeding Pedigrees- family lineages Evolu$onary trends 1

2 1.How are genes passed on to our offspring? 2. Sperm carry ½ and eggs ½ of gene$c code. 1. How are sperm & eggs produced? 2. Meiosis germ cells divide to produce haploid cells (1 set of chromosomes) 3. Haploid =1N 2. Meiosis has 2 divisions to reduce chromosome number 2

3 2. What are the phases of meiosis? Meiosis I Prophase I- Crossing over of alleles occurs! Metaphase I- homologous chromosomes side by side Anaphase I- ho. chrom. separate (not chroma$ds) Telophase I- 2 cells with 2 chroma$ds of every chromos. Meiosis II Prophase II- nothing happens Metaphase II- chromo align single file Anaphase II- chroma$ds pull apart Telophase II- 4 total cells w/ 1 copy of each chromo. 3

4 1N + 1N = 2N (a diploid cell) 46 XX= female 46 XY = male 23 pr homologous chromosomes What are the results of meiosis? 4 cells Gene$cally different Haploid (1N) In females, only one egg is used 4

5 What happens if chromosomes don t separate properly? Nondisjuc$on results in trisomy or monosomy 5

6 Dragon gene$cs ac$vity to learn basic vocabulary Check for understanding following ac$vity: BB Bb Bb Allele/gene Genotype/phenotype Mate your dragons Punne` squares Designed to PREDICT outcomes (expected ra$os) 6

7 Single gene crosses monohybrid: Aa x Aa Or : AA x Aa Or Testcross: aa x A Cys$c fibrosis Due to a recessive allele (ff) Faulty membrane protein does not regulate NaCl Cells create mucous around them/breeding ground for bacteria Chromo #7 Hun$ngton disease Due to a dominant allele Late onset (35 years+) Protein (hun$ng$n) destroys nerve cells Due to a repeat of more than 21 CAG in a gene Chromosome 4 (discovered in 1983) Maracaibo, Venezuela- Hun$ngton research 7

8 Di- crosses probability problems Rh factors- effect on fetus- protein on RBC- rh from RHESUS monkey- Rh neg makes an$bodies against Rh protein- Rh is important during fetal development Albinism- due to recessive alleles Review terms Alleles/gene Genotype/phenotype Homozygous/heterozygous Probability Offspring/ F1/F2 genera$ons Dominant/recessive Quiz 1. Explain how an allele is related to a gene. 2. What is the rela$onship between a genotype and a phenotype? 3. Which of the following combina$ons are homozygous? BB Bb bb 8

9 4. T- tall t short Y yellow y- green Cross a plant that is heterozygous tall and homozygous for green seeds with a plant that is short and is also homozygous for green seeds. List the genotypes and ra$os for the above cross. List the phenotypes and ra$os for the above cross. Codominance Both alleles of a gene express themselves= both proteins are produced Examples: AB blood type (protein A and protein B ) Sickle cell trait ( point muta$on in hemoglobin)- produces 3 phenotypes- normal, trait, anemia Blood type importance Your immune system makes an$bodies against foreign proteins. An$body A a`acks blood type A An$body B a`acks blood type B An$bodies A & B a`ack blood type AB An$bodies A & B DO NOT a`ack blood type O 9

10 blood types- mul$ple alleles Phenotype (protein) Blood type A Blood type B Blood type AB Genotype (alleles) AA or AO BB or BO AB Blood type O OO Blood type lab An$bodies can cause blood to clump (agglu$nate) This is how blood is typed for accuracy for transfusions. What is the importance of sickle cell trait? Evolu$onary advantage to survive Malaria heterozygote advantage- NS (trait) S cells sickle and the protozoan is killed 10

11 Video clip on sickle cell evolu$on Normal RBCs vs. Sickle RBCs phenotype Normal blood cells ½ normal & ½ can sickle all can sickle genotype NN NS SS Incomplete dominance 2 alleles blend their traits and produce a 3 rd phenotype Examples: Palamino horses (ncomplete & polygenic) Tay- Sachs enzyme levels (enzymes, some enzymes, no enzyme) 11

12 Some flowers MAKE SURE YOU BRING YOUR GENETICS DISEASE INFO SHEET WITH YOU TO WORK ON COMPUTERS TOMORROW. X linked genes Genes that are located on the X chromosome only Examples Hemophilia Red- green color blindness Duschene muscular dystrophy Calico cats ALD (Lorenzo s oil disease) 12

13 hemophilia Hemophiliacs lack protein factors for cloung. Pedigrees 13

14 Red green color blindness Muscular dystrophy 14

15 Image of Calico cat- x linked & epista$c genes Epista$c genes Genes that cancel out other genes Environmental effects on genes 15

16 Polygenic inheritance More than one gene codes for a trait Examples skin color, eye color, height, hair color Genes are addi$ve Muta$ons Can be neutral, harmful or beneficial. Point muta$ons: subs$tutes a base Frameshiv muta$ons: add or delete a base Chromosomal changes 16

17 Dele$on: Cri- du- chat Duplica$on: Fragile X Transloca$on 17

18 Nondisjunc$on- Down s syndrome $meline Gene$cs introduc$on to Mendel & vocabulary via dragon gene$cs Single gene Punne`s Mul$ple gene Punne`s Codominance Incomplete dominance Epista$c genes Chromosomal muta$ons 18