Biology Lab 1000- LAB 9 Mendelian Genetics PDF

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Summary

Professor Jennifer Juarez-Ayala
Week 9 - course work
you will learn about Genetics, Laws of Chromosomal arrangement in a gamete, alleles, genotype, phenotype, Homozygous and Heterozygous
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LAB 9: MENDELIAN GENETICS Genetic Inheritance of Traits Genetics-is the study of hereditary transmission and variation ❖ Gregor Mendel is considered the “father of genetics”, yet he didn’t know about chromosomes, genes or DNA ➢ ONLY KNEW traits were passed onto offspring ❖ What we know ➢ Hereditary information is encoded in GENES ➢ Sequences of DNA code for a single pattern ➢ Chromosomes are long strands of DNA containing hundreds or thousands of genes ➢ Mitosis produces exact copies of diploid cells ➢ Meiosis reduces diploid cells to haploid cells & results in the production of gametes ➢ Homologous chromosomes are chromosomes that we get from both mom and dad ➢ Alleles are different forms of genes ❖ Two Laws of Chromosomal arrangement in gamete ➢ 1. Law of Segregation ■ During production of gametes two variations (alleles) of one gene segregate s o that offspring acquire one allele from each parent during meiosis (Anaphase 1), allowing for predictable ratios of traits in the offspring ➢ 2. Law of Independent Assortment ■ When 2 or more genes (traits) are inherited, the alleles of those different genes assort Independently into gametes ● Allele that a gamete received for another gene ◆ You can determine this by using these two laws ➢ 1. The ratio of different gametes any given genotype can produce ➢ 2. The ratio of offspring genotypes and phenotypes produced by the cross of any two individuals

ALLELES & GENES ❖ Genes are portion of DNA, and they have the ability to code for a characteristic -traits ➢ Many traits are coded by interactions of more than one gene ❖ Human have 46 chromosomes ➢ Chromosomes are made up of DNA and Protein --condensed unit of DNA ➢ Genetic code represented by chromosomes ➢ You inherit 23 chromosomes from your mother and 23 from your father ❖ Each parent contributes and allele- a variant of a gene ➢ Alleles could be the same form of the gene or different forms of the gene

➢ Two alleles you inherit, together, forma gene that determines whether you have a trait or not ➢ Alleles are typically represented by letters ■ Matters what you represent as a capital or lowercase letter ● If you use a capital letter to represent an allele, it means its dominant ◆ If one or both of the alleles you ing=herited for a trait are dominant, then it will be expressed ● If you use a lowercase letter to represent an allele, that means it’s a recessive allele ◆ Not expressed unless there is no dominant allele present ➢ You have two allele copies, so you can have multiple combinations ■ Ex. TT, Tt or tt, ● This is called genotypes- genetic makeup ◆ Genotypes can help determine a phenotype (physical characteristic) ➢ Ex. PTC TATERS (dominant trait) ■ This trait only takes the presence of one dominant traits ● TT or Tt can have this trait because this traits only needs at least one dominant trait

Monohybrids and the Punnett Square Guinea Pigs ❖ Hairless Guinea pig ➢ They receive genes from both their parents ■ An allele is a form a gene and often represented by a letter , in this case, we’ll use the letter h for hair ➢ Hairless guinea pig has two recessive alleles for the trait of having or not having hair ➢ A recessive allele represented by a lowercase allele ■ Recessive- means that the allele will not usually show up ● Only way it will show up is if there is no dominant allele present ➢ Dominant allele is represented by a capital letter and it does show up ■ Hairless guinea pig does not have a dominant gene for hair and that’s why the recessive traits of not having hair shows up ● Hairless guinea pig’s genotype can be represented by hh ● Guinea pig that does have hair can be represented by HH OR Hh ◆ Only takes one dominant allele (H) for trait to show up ➢ Genotype of HH or hh is considered Homozygous (same) ■ HH is called homozygous dominant ■ hh is called homozygous recessive ➢ Genotype of Hh is considered heterozygous (different) ❖ Monohybrid Cross

➢ Mono means 1 because it focuses on one trait→ In this example it will be the trait of hair ■ Punnett square needs to be created ● Going to cross two heterozygous guinea pigs ■ Steps ● 1. Figure out the genotypes of the parents ● 2. Place one parent along the top of the punnett square & other along the left side of square ◆ H

h

H

h

H

HH

Hh

h

Hh

hh

H h ●

3. Coss them ◆

◆ Genotypes are: HH, Hh, and hh ◆ Phenotypes: babies who will have hair- HH & Hh Babies who will not have hair- hh

Exercise 1: Snurfle Meiosis and Genetics- The law of Segregation and Monohybrid Crosses ● Incomplete dominance- heterozygous individuals express a phenotype that represents a mixture of the two alleles ● Co-Dominance- heterozygous individuals express a phenotype that maintains both alleles in their original form ● Ex or incomplete and co-domince ○ w=white petal flower ○ r= red petal flower ■ incomplete dominance- pink flower ■ Codominance- white flower with red spots BioMan ( Genetic Interactive) ❖ Letters on the top & side of the Punnett Square represent gametes (sperm and eggs) ➢ Each letter is a possible sperm or egg ❖ Fertilized egg is called a ZYGOTE

G

g

G

GG

Gg

g

Gg

gg

❖ Genotype- genetic make-up of an organism ➢ Genotypes in punnett Square: GG, Gg, gg ❖ Phenotype- characteristic or appearance of the organism ❖ Dominant allele is represented by a Capital letter ➢ G ❖ Recessive allele is represented by a lowercase letter ➢ g ❖ Homozygous means an organism has 2 copies of the same allele in its genotype ➢ GG, gg ❖ Heterozygous means an organism has two different alleles in its genotype ➢ Gg ❖ Zygote goes through cell division many times to make all the cells that make up the baby Question 1: Snurfle fur color exhibits the complete dominance model, resulting in either yellow or green fur. What additional phenotype might we expect if fur color exhibited a model of co-dominance? Answer: Green and Yellow blotched Question 2: Snurfle fur color exhibits complete dominance model, resulting in either yellow or green fur. What additional phenotype might we expect if fur color exhibited a model of Incomplete dominance? Answer: solid greenish-yellow Question 3: two heterozygous (Gg * Gg) snurfle parents mate and produce one Snurfle baby. What is the chance of them having a baby that is homozygous recessive? Answer: 25% because.. Homozygous means an organism has 2 copies of the same allele in its genotype Recessive represented by lowercase letter The genotype that fits this statement is gg and there is only one

G

g

G

GG

Gg

g

Gg

gg

Exercise 2: Snurfle Meiosis and Genetics 2- Recombination, Law of Independent Assortment, and Dihybrid Crosses BioMan: Crossing over ❖ Why does crossing over increase Diversity? ■ Meiosis Summary ● At the start at Meiosis, you have 1 DIPLOID cell ● At the end, you have 2 HAPLOID cells ● At the end of meiosis 2, you have 4 HAPLOID GAMETES QUESTION 1: so far, we have examined a cell that DOES NOT do crossing over. What is true about such a cell? Answer: b. It will produce a limited variety of gametes with certain alleles being always passed on together Question 2: So far, we have examined… Answer: b. A cell that does NOT do crossing over Question 3: Genes that are usually inherited together because they are on the same chromosome are known as.. Answer: a. Linked genes Question 4: What does CROSSING OVER occur? Answer: Prophase 1 of Meiosis 1 Question 5: What exchanges DNA during crossing over Answer: Homologous chromosomes Question 6: If the cell to the right were to cross over one time during Prophase 1 of Meiosis, how many genetically distinct gametes would be produced? Answer: 4 Question 7: If the cell to the right does NOT cross over, how many genetically distinct varieties of gametes are produced ? Answer: 2 Question 8: These cells have ____ chromosomes as results of crossing over Answer: recombinant Question 9: Which of the following statements are true about crossing over? Answer: 2 and 3 only

BioMan: Independent Assortment Question 1. When does independent assortment occur? Answer: metaphase 1 of meiosis

Question 2: Which of the following statements is true as a result of independent assortment? Answer: the alignment of the top pair of chromosomes will NOT affect the alignment of the bottom pair Question 3: How does independent assortment during metaphase 1 help to produce diverse gametes? Answer: all of these Question 4: How does independent assortment during METAPHASE 2 help to produce diverse gametes? Answer: sister chromatids of individual chromosomes line up randomly, resulting in a variety of possible genetic combinations in gametes

BioMan: Random Fertilization Question 1:Which of the following are true? Answer: 1 and 2 Question 2: when doing a dihybrid cross, how many genes are examined? Answer: 2 Question 3: What goes on the top and left side of the Punnett Square Answer: The gametes of one parent go on the top and the gametes of the other parent go on the left side Question 4: when filling in a punnett square, what goes inside the boxes? Answer: the genotypes of the offspring Question 5: what process in meiosis is represented by FOIL? Answer: independent assortment Question 6: which of the following is true? Answer: Both 1 and 2 Question 7 : Which of the following is the correct genotype for the following Snurfle baby? Answer: ggff Question 8: which of the following is the correct phenotype for the following snurfle baby? Answer: green fur with fins BioMan: Take a Quiz Question 1: Which of the following is true about crossing over, independent assortment, and random fertilization? Answer: they all increase the diversity of potential offspring

Question 2: what process is depicted in the animation shown? Answer: crossing over Question 3: When does crossing over occur? Answer: prophase 1 of meiosis 1 Question 4: which of the following is a true statement? Answer: independent assortment occurs b/c chromosomes can line up in diff. Ways during metaphase 1 and metaphase 2 of meiosis Question 5: Which is the correct way to do FOIL for the following parents: GGFf * GgFf? Answer: A Question 6: FOIL is most closely associated w/ which of the following processes? Answer: independent assortment , because it shows that genes on different chromosomes randomly assort into gametes during meiosis Question 7: choose the correct gametes for the following genotypes if independent assortment occurs Answer: Sperm: GF, GF, gF, gf Eggs: GF, Gf, gF, gf Question 8: what would be the genotype of the individual found in the box labeled Q? Answer: ggFF Question 9: If the yellow is dominant to green and having NO fins is dominant to having fins, what would be the phenotype of individual Z Answer: yellow w/ no fins Question 10: which of the following statements are true? Answer: 1,2, and 3...