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AP Biology. Mendelian Genetics Part 1. What are genes? DNA segments, inherited from our parents, that code for proteins What is a polypeptide? A protein What processes produce proteins? Transcription and translation. Who was Gregor Mendel? Known as the “Father of Genetics”
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AP Biology Mendelian Genetics Part 1
What are genes? • DNA segments, inherited from our parents, that code for proteins • What is a polypeptide? • A protein • What processes produce proteins? • Transcription and translation
Who was Gregor Mendel? • Known as the “Father of Genetics” • He was an Austrian monk • He was the cook for the monastery, so he had his own garden • He observed, grew, and experimented with pea plants
What is a character? • An inheritable physical feature • Eye color or hair color would be examples • What is a trait? • The variation of a character • Blue eyes or black hair • Two alleles are inherited, one from each parent, in order to create the variation
What is an allele? • Different versions of a gene • A gene is a distinct DNA nucleotide sequence that can make one protein • There can be different versions of the same gene, but they all make the same thing (ex. Eye color) • Each trait must have two alleles
What are dominant alleles? • They are the genes with the genetic information • They are represented with capital letters (Tt) • What are recessive alleles? • They are the genes without genetic information • They are represented with lower case letters
What is a true or pure breed? • Organisms with only one type of allele for a trait • The alleles are homologous (the same) • PP or pp
What is hybridization? • The creation of an organism that has two different types of alleles for a trait • The organism is referred to as a hybrid • It has heterozygous alleles
What is a phenotype? • The physical traits that can be seen • Blue eyes • Type A blood • Black hair
What is a genotype? • The genetic or DNA make-up for the trait
How can you determine a genotype? • Perform a test cross • Mate a homozygous recessive with the unknown genotype • That way no genetic information will be covered up by a dominant allele
What is a Punnett square? • A chart that shows all the possible genotypic outcomes that can occur from the mating of two organisms Monohybrid cross 4 squares Dihybrid cross 16 squares Trihybrid cross 64 squares
What is Mendel’s Law of Segregation? • During Anaphase I and II, homologous chromosomes of sister chromatids will move independently of each other
What is Mendel’s Law of independent Assortment? • Variations are possible on sets of chromosomes, because chromosomes line up during Metaphase I and II independently and randomly
What is probability? • Chance • The likelyhood of a certain outcome • The range is 0 to 1 • O is 0% and 1 is 100% • .5 would be 50%
What is the best way to assess the probability in a mating cross? • Use the Rule of Multiplication • Using the parents’ genetics multiplied together to predict the genetics of the offspring
Dominant phenotype, unknown genotype: PP or Pp? Recessive phenotype, known genotype: pp Test Cross If Pp, then 1 2 offspring purple and 1 2 offspring white: If PP, then all offspring purple: p p p p P P Pp Pp Pp Pp P P pp pp Pp Pp
Key Maternal set of chromosomes Possibility 2 Possibility 1 Paternal set of chromosomes Independent Assortment Two equally probable arrangements of chromosomes at metaphase I Metaphase II Daughter cells Combination 3 Combination 2 Combination 4 Combination 1
AP Biology Mendelian Genetics Part 2
What produces the phenotype in an organism? • The expression of proteins • What determines the proteins that will be constructed? • Nucleotide sequences that form the codons
What is incomplete dominance? • Genetic information is blended • The dominant phenotype is not completely covering over the recessive • Both phenotypes are seen in a blended version
What is complete dominance? • The dominant allele has all the DNA nucleotide information to produce a fully functioning protein • This completely suppresses the recessive allele, so that it is not seen at all
What is codominance? • Both alleles are seen and are not blended • They both are expressed equally
What are multiple alleles? • There are several versions of the same basic gene • How do multiple alleles work in blood types? • Glycoproteins are produced on the surface of the red blood cells • One type of glycoprotein is Type A; another type of glycoprotein is Type B • If there is no information for making the glycoprotein, then it is Type O
What is Hemophylactic Shock? • If two blood types are mixed, the glycoprotein “hands” will not recognize each other • One of the blood types will be perceived as foreign, and the white blood cells will begin killing those blood cells
What is the universal donor? • This blood type is acceptable by all blood types • Type O is the universal donor • It has NO glycoproteins on the surface of the cell, therefore, there is nothing for other cells to view as “unrecognizable”
What is the universal recipient? • This is the blood type that will accept ANY other blood type • Type AB is the universal recipient • It has glycoproteins that will recognize the glycoproteins on any other red blood cell
What is pleiotropy? • One gene affects many phenotypes • Sickle Cell Anemia is a good example • This gene affects the red blood cell shape, oxygen carrying ability, resistance to Malaria, etc.
What is epistasis? (one source [epi] affects another location [stasis] • A gene at one location on a chromosome affects a gene at another location on the chromosome • The phenotypes of hair would be a good example • Several genes interact to affect hair color, shape, thickness, texture, etc.
What is the ratio for most dihybrid crosses? • 9:3:3:1 • What is the ratio when epistasis occurs? • 9:3:4
The number of alleles received are referred to as Quantitative Characters • What is polygenic inheritance? • Many different degrees of phenotypic outcomes • What determines the outcome? • The number of alleles you inherit from your parents for that trait • Skin color is a good example (how many copies of the same gene were received by the offspring)
What is the norm of reaction? • The majority of organisms that fall on the bell curve for the trait
What is referred to by the term “multifactorial”? • Many environmental factors affect one phenotype • This concept is often referred to as “nature vs nurture, or “genetics vs the environment” • Most agree that it is about a 50/50 blend • Height • Intelligence • Weight
3’ T A C C A G C C G G T A A T A G G G A C C A T T 5’ DNA TEMPLATE 5’ A U G G U C G G C C A U U A U C C C U G G U A A 3’ mRNA METH VAL GLY __ HIST TYR __ PRO TRP __ __ ___ ___ PROTEIN 3’ U A C C A G C C G G U A A U A G G G A C C A U U 5’ ANTI – CODON Sequence Does the DNA Sequence (Million Dollar Blueprint) look like the Anti-codon Sequence? Remember, this is how the ribosome “knew” the Amino Acid was Correct.
