CP Biology Ch. 11 - Genetics Name ______

Amatuzzi 16

Mendel’s 3 Laws of Inheritance:

1.  Law of Dominance

2.  Law of Segregation

One Factor (Hybrid) Cross

Cross a heterozygous black (black is dominant) cat with a white cat

Parent genotypes:

Ratio of phenotypes in offspring

Test cross – find genotype of dominant phenotype

Find the genotype of a tall (dominant) plant.

a)  Cross with short (recessive)

b)  If Tall parent is homozygous, offspring are short.

c)  If Tall parent is heterozygous, offspring are short.

3.  Law of Independent Assortment

Two-Factor (Dihybrid) Cross:

Practice a Dihybrid cross:

F= fat f = thin; E = black e = brown

Cross a heterozygous fat, heterozygous black mouse with a heterozygous fat, brown mouse.

Parent genotypes: ______x ______

Count of phenotypes in offspring:

Fat and black

Fat and brown

Thin and black

Thin and brown

Ratio of phenotypes

11.2  Other Patterns of Inheritance

A. Incomplete dominance

Pink four o’clock flower

Blue Andalusian chicken

B. Codominance

Roan horse

C. Multiple allele – More than two alleles exist in the population.

Human blood groups – 3 alleles

Alleles A and B are codominant

Allele O is recessive

Blood Type / Genotypes
A
B
AB
O

Practice multiple allele crosses:

A man with blood type AB marries a woman A man with blood type B whose father was type O

heterozygous for blood type A. What possible marries a woman with type A whose mother was

blood types might their children have? type AB. What possible blood types might their

children have?

Genes and the Environment

Examples

Sex-Linkage - genes on sex chromosomes (usually X)

Thomas Hunt Morgan

Sex-linked traits in Humans

– more common in males than in females

Color-blindness in humans

Practlice: A woman whose father was color-blind marries

a man with normal vision. What are the chances that their

child will be color-blind? Which gender has this risk?

Hemophilia

Duchenne Muscular Dystrophy

Eye color in fruit flies

Autosomal Gene disorders in Humans

Recessive: Cystic fibrosis

PKU – phenylketonuria

Sickle Cell Disease

Tay-Sachs Disease

Dominant: Huntington’s Disease

Polygenic inheritance

Examples

Hybrid Vigor

Examples

Polyploidy

Lethal alleles

Chapter 12: DNA Function – How do Genes Work?

‘Gene Expression’ or ‘Protein Synthesis’ – gene is turned on and working

1)  Transcription

2)  Translation

Translating the code

codon

DNA

mRNA

amino acids

QUICK BASICS HOW DNA WORKS Name______

How does DNA control all life functions?

1. DNA stores instructions to make which kind of molecule? ______

a.  One type of these molecules acts as enzymes. What is their function? ______

2. Which part of the DNA molecule functions as the CODE? ______

“Central Dogma of Molecular Genetics”

RNA copies the code for a gene from DNA and uses it to make a protein.

Step 1) Copy the code: TRANSCRIPTION (DNA-to-RNA)

1.  DNA molecule opens at beginning of a ______

2.  Free RNA ______match to their complementary DNA bases

3.  C à _____; A à ______

4.  no T in RNA; U = ______

5.  forms a molecule of ______RNA

6.  mRNA leaves ______and goes to ______

Step 2) Use the code to make a protein: TRANSLATION (RNA-to-protein)

1 There are ______(#) DNA bases, and ____(#) different amino acids.

2. Each amino acid is coded for by a set of ____(#) mRNA bases, called a ______

3. Each transfer RNA (tRNA) molecule carries one specific ______

4. Amino acids line up in the ribosome according to the code on the ______molecule

5. A chain of amino acids forms a ______, which then folds into a functional ______.

Transfer RNA (tRNA)

·  3 bases on tRNA complement 3 bases on ______.

·  Specifies sequence of ______

Ribosome is made of protein and ribosomal RNA (rRNA)

DECIPHERING the DNA CODE

Code is carried on mRNA in sets of _____ bases, called ______

a. Each codon codes for one ______

b. The sequence of codons = the sequence of ______

c. A chain of amino acids makes ______

Chart of mRNA codons for amino acids. Note: Includes “start” and “stop” codes.

USE THE CHART: Here is a short piece of DNA coding for a protein.

T A C C T G G A T A T C

1.  Write the mRNA bases in sequence that correspond to the DNA. Use sets of three (codons)

______

2.  Use the chart to find the sequence of amino acids coded by this mRNA molecule.

______

6