applied biology genetics notes. genetics introduction genetics is the study of heredity heredity...
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Genetics Introduction
• Genetics is the study of heredity
• Heredity explains why you look like your parents or siblings (similar traits)
• Traits (ex. Color, shape) are inherited or passed down to offspring in genetic crosses
Essential Vocabulary!
• Gene – parts of DNA that control traits
• Gregor Mendel – “Father of Genetics”, studied inheritable information & performed plant-cross experiments
Dominant vs Recessive
Dominant gene – trait ALWAYS shows itself
Recessive gene – trait hidden when dominant gene is present
Allele – forms of a particular gene (we use caps & lower case letters)
(R = round and r = wrinkled…….but both code for shape)
Homozygous vs. Heterozygous
• Homozygous – 2 of same allele for a trait (RR or rr)
• Heterozygous – 2 different alleles for a trait (Rr)
Phenotype vs. GenotypePhenotype vs. Genotype
• Phenotype – physical observable trait (shape, color ect.)
• Genotype – genetic make-up, combination of alleles (RR, Rr, rr)
Genotype
Phenotype (purple)
Solving Genetics ProblemsSolving Genetics Problems
1. Designate letters for traits (R=Round, r=wrinkled)
2. Determine parent alleles
3. Set up Punnett square
4. Fill – in Squares
5. Determine possible offspring genotypes & Phenotypes
Practice ProblemBlack hair (B) is dominant over brown hair (b). A man heterozygous for black hair and a woman with brown hair have children. What are the genotypes and phenotypes of their offspring?
Step #1 B = black b = brown
Step #2 Dad = Mom = Step #3 (punnett square)
Step #4 (fill-in offspring squares)
Step #5 (Genotypes & phenotypes)
Blood Typing Genetics(Codominance & Multiple Alleles)
• In simple genetics…there are usually 2 alleles– 1 dominant (R) & 1 recessive (r)
• In Codominance…neither allele is dominant over the other!
• Since they are COdominant…they both show up in the heterozygous phenotype!
Blood Typing Genetics (cont.)
• Usually in simple genetics problems we have:– 1 Dominant Allele– 1 Recessive Allele R or r
• In Blood typing, we have:–2 Dominant Alleles = A & B–1 Recessive Allele = o
EXAMPLE: Blood Types!
Blood Typing - Codominance• In humans, there are 4 possible blood
types: A, B, AB, and O.
• Type O individuals are considered to be the “universal donors”, whereas type AB individuals are said to be “universal recipients”!
Blood Type Genotypes
Type A Blood– AA is homozygous– Ao is heterozygous
Type B Blood– BB is homozygous– Bo is heterozygous
Type AB Blood– AB (this is the co-dominant blood type!)
Type O Blood– oo (only 1 way to have Type O blood because o is
recessive!)
Blood Typing – Practice Problem
A man heterozygous for Type A blood and woman homozygous for Type B blood have children. What are the possible genotypes and phenotypes of their offspring?
Practice Problem #2Two babies are ready to go home from the hospital…
Which baby belongs to which parents?
• Here’s what you know about the babies:– Baby A bas blood type A– Baby B has blood type O
Parents #1 - Father (Homozygous Type A) & Mother (Type O)
Parents #2 - Father & Mother (Heterozygous A)
Sex Linkage – Hemophilia
Some traits are carried on the X chromosome!! Hemophilia is the most well-known sex-linked disease!
Males = X Y
Females = X X
Hemophilia Lacking the ability for blood to clot…can’t stop bleeding
Possible Genotypes:
Hemophilic Male Genotype = X Y
Hemophilic Female = X X
Normal Male Genotype = X Y
Normal Female Genotypes = X X X X (CARRIER)
Practice Sex Linkage (Hemophilia)
ProblemA man with hemophilia and a normal women (but carrier for hemophilia) have a child. What are the possible genotypes and phenotypes of their offspring?
Man = X Y
Woman = X X
Offspring Genotypes:
Offspring Phenotypes:
Human GeneticsKaryotype - the complete set of chromosomes in a species. Can show chromosomal disorders such as:
1.Down Syndrome (Trisomy 21)
2.Turner Syndrome (X missing pieces)
3.Klinefelter Syndrome (XXY)
Chromosomal Disorders occur due to NONDISJUNCTION – error in meiosis where chromosomes don’t separate correctly during anaphase!