2 How are haploid gamete cells produced from diploid cells? Your parents have 46 chromosomes each and you have 46 chromosomes.If you got half of your genes from each parent, how did this happen?How many chromosomes do a sperm and an egg have?
3 MeiosisThe process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell that become haploid cells.Involves two distinct divisions; Meiosis I and Meiosis IIOne diploid cell becomes 4 haploid cells
4 Crossing Over Prophase I Homologous chromosomes exchange alleles Produces new combinations of allelesCauses randomness in gamete formation
5 Meiosis IProphase I- Chromosomes pair with same homologous chromosomes to form a tetrad.Metaphase I- Homologous chromosomes meet in the middle and spindle fibers attach.Anaphase I- Homologous chromosomes are pulled apart by spindle fibersTelophase I- Nuclear membrane forms around separated chromosomes to form two nuclei.Cytokinesis- The diploid cell separates into two haploid cells.
7 Meiosis II starts with two haploid daughter cells Prophase II- haploid chromosomes with sister chromatid are in the cytoplasm.Metaphase II- chromosomes meet in the middle of the cellAnaphase II- Sister chromatid are pulled apart by spindle fibersTelophase II- Nuclear envelop forms around the chromosomesCytokinesis- Results in 4 haploid daughter cells
11 Place these items into your Venn Diagram: Produces diploid cellsProduces haploid cellsType of cell divisionCreates identical cellsSeparates homologous chromosomesSeparates chromatidsCreates “daughter” cells2 rounds of cell divisionOnly 1 round of cell divisionCreates unique cellsBegins with diploid cellsCreates gametesCreates “body cells”Has crossing over
12 GenesGenes are the characteristics contained in the DNA of every cell.Each gene is made up of 2 alleles- one inherited from each parent.For instance you may have one brown eye allele inherited from your dad and one blue eye allele inherited from your mom.
13 Kinds of alleles Dominant- Recessive- These alleles always determine the physical feature of the individual.These alleles are represented by a capital letter.Recessive-These alleles only determine the physical feature of the individual when there is no dominant allele.These alleles are represented by a lower case letter.
14 Genotype and Phenotype The genotype of an individual is the description of the actual genetic information for a trait.The phenotype of an individual is the physical feature observed.
15 Allele CombinationsEvery gene is made up of two alleles-one from each parent.If both alleles are the same, the gene is called homozygous. (BB or bb)If the alleles are different, the gene is called heterozygous. (Bb)
16 Label the following as homozygous dominant, homozygous recessive, or heterozygous. BBAannKkGGffqqHh
17 Probability and Punnett Squares Meiosis separates the alleles of a parent into different sex cells (gametes).For instance: Dad is heterozygous for Brown hair, with a blond hair allele as the recessive. (Bb).Through meiosis, these alleles are copied and separated into 4 sperm.bBbB
18 Single Trait CrossingWhat kind of offspring (kid) would two parents have?A Punnett Square can help you find out!Example: Dad is heterozygous (Bb) for Brown hair over blond hair. Mom is also heterozygous (Bb) for brown hair over blond hair.
19 Set up the SquareDad’s AllelesBbBMom’s allelesb
20 Set up the Square B b B BB Bb b Bb bb Dad’s Alleles 4 possible offspringMom’s allelesbBbbb
21 What do these results mean? ¼ or 25% chance of an offspring with homozygous dominant genes for brown hair.½ or 50% chance of an offspring with heterozygous genes for brown hair.¼ or 25% chance of an offspring with homozygous recessive genes for blond hair.
22 You try it!1. Dad is heterozygous for Brown eyes over blue eyes. (Ee) Mom is homozygous recessive with blue eyes. (ee) What are the probabilities for the children’s genotypes. What are the probabilities for the children’s phenotypes?
23 Set up the SquareDad’s AllelesEeeMom’s allelese
24 Dad’s AllelesEeeEeee4 possible offspringMom’s alleleseEeee
25 ½ or 50% of the children would inherit heterozygous genes for Brown eyes (Ee) ½ or 50% of the children would inherit homozygous recessive genes for Blue eyes (ee)
26 Hmmm…Is it possible for two Brown haired parents to produce a blond child? Explain.Is it possible for 2 blue eyed parents to produce a brown eyed child? Explain.Can you figure out your genotype for hair color? How do you know?
27 Review Questions How is meiosis related to heredity? What is the difference between heterozygous, homozygous dominant, and homozygous recessive?Is it possible for two brown haired parents to produce a blond child? Explain.
28 Review cont… What is the difference between genotype and phenotype? What are the chances that two heterozygous parents with Brown hair(Bb) produce a child that is also heterozygous?
29 Review cont…In pea plants, round peas are dominant over wrinkled peas. (R and r). What would the offspring of a homozygous dominant, and a homozygous recessive cross look like?If the offspring from question #6 were to pollinate each other (as plants often do), what would be the genotype probabilities for the offspring?
30 Two Trait CrossesWhen looking at two different genes in the same cross, 4 alleles are dealt with.For instance, a heterozygous haired(Bb), and homozygous recessive eyed(ee) parent would be Bbee.Through meiosis, there would be 4 possible allele combinations in the sex cells.
31 FOIL!Just like in math class, the first, outside, inside, and last rule can help you remember.B b e eThese alleles would produce these four combinations.Be Be be be
32 What does a two trait cross look like? Suppose two parents who are both heterozygous haired and heterozygous eyed produce a child. What are the possible genotypes and phenotypes in the offspring?
33 You try it!A tall (TT) pea plant that produces yellow colored peas (Yy) crosses with a short (tt) pea plant with green colored peas (yy). Create the Punnett square and list the probabilities of each genotype.