Download Chapter 4 – 5 Genetics Study Guide 1. In Mendel`s experiment, the P

Chapter 4 – 5 Genetics Study Guide
1. In Mendel’s experiment, the P generation was one tall plant and one short plant. The P
generation had offsprings which was the F1 generation. The F1 generation were all tall plants.
The F1 generation then had offsprings which is the F2 generation. The F2 generation had 3 tall
plants and 1 short plant. Therefore 75% tall and 25% short.
2. The P generation were purebred. The F1 generation was hybrid because they had one of the
alleles for tall plants and one for short plants.
3. Factors that control traits are called genes. Different forms of genes are called alleles.
4. TT means two dominant alleles, purebred, and homozygous. Tt means one dominant, one
recessive alleles; hybrid, and heterozygous. tt means two recessive alleles, purebred, and
homozygous. Dominant traits will also show if the dominant allele is present. T means
dominant, t means recessive.
5. Probability-a number that describes how likely it is that an event will occur.
6. Punnett Square- a chart that shows all the possible combinations of alleles that can result from
a genetic cross.
7. See Punnett Square example page 121 and 123.
8. Phenotype- an organism’s physical appearance or visible traits. Genotype- an organism’s
genetic makeup or allele combinations.
Homozygous- an organism that has two identical alleles for a trait. Ex. TT
Heterozygous- an organism that has two different alleles for a trait. Ex. Tt
9. In some traits, neither allele is dominant. In this case, both alleles are expressed and this is
called codominance.
10. According to the chromosome theory of inheritance, genes are carried from parents to their
offsprings on chromosomes.
11. Meiosis is the process by which the number of chromosomes is reduced by half to form sex
cells – sperm and eggs. During Meiosis, the chromosome pairs separate and are distributed to
two different cells. The resulting sex cells have only half as many chromosomes as the other
cells in the organism.
12. The offspring gets the normal number of chromosomes – half from each parent. The body
cells of humans contain 23 chromosome pairs or 46 chromosomes.
13. Chromosomes are made up of many genes joined together like beads on a string.
14. Single gene with more than two alleles- traits controlled by a gene that has three or more
forms. Example: Blood type.
15. Female- two X chromosomes; Male – one X and one Y chromosome.
16. Carrier- a person that does not display a trait because they have one dominant and one
recessive allele.
17. The genetic code is found along the Nitrogen bases along a gene.
18. Be able to construct a Punnett Square and explain the genotype and phenotype of each.