Chapter 11 & 12Name ______
Heredity & DNALife Science
- Trait – A characteristic that an organism can pass on to its offspring is called a trait. Traits are things like hair color, eye color, skin color, seed shape, height, etc. (214)
- Heredity & Genetics – The set of traits you receive from your parents is called heredity.
Genetics is the study of heredity. (214)
- Gregor Mendel – Gregor Mendel was an Austrian monk who is often called “the father of genetics”. Through many years of experiments in breeding pea plants Mendel arrived at very important conclusions about genetic inheritance. His ideas led to the entire science ofgenetics. (215)
- Pollination – Flowering plants reproduce by pollination. During pollination, pollen grains containing sperm from the male part of the plant (the anther) are carried to the female part of the plant called the ovule. Fertilization occurs when a sperm from the pollen grain travels to an egg in the ovule. When pollen fertilizes eggs from the same plant this is called self-pollination. When pollen fertilizes the eggs of a different plant (carried by wind, insects, etc.) this is called cross-pollination.
- True-breeding – A plant that always produces offspring with the same form of a trait when self pollinated is called a true-breeding plant.
- Genes & Alleles – A segment or unit of DNA that determines traits (heredity) is called a gene. Different forms of the same trait (gene) are called alleles. Organisms have at least two alleles for each gene, one fromeach parent.(218)
- Dominant Allele – A dominant allele is a stronger form of a gene that, when present, covers
up the appearance of the recessive allele.Dominant alleles are written as a capitol letter. (218)
8. Recessive Allele – A recessive allele is a weaker form of a gene that is hidden when combined
witha dominant allele. Recessive alleles are written as a lower case letter. (218)
9. Phenotype – The form of a trait that is displayed in an organism (what you see) is called the
phenotype.It is the physical appearance of the inherited traits caused by the combined alleles.
Examples include: blue eyes or brown eyes, tall or short, black fur or white fur, purple flower
or white flower, etc.. (219)
10. Genotype – An organisms genotype shows the actual alleles of the gene. Genotypes that have
the same form of the trait in both genes are called homozygous (examples BB, PP). Genotypes
that have differentforms of the trait for each gene are called heterozygous(examples: Bb, Pp).
11. Punnett Square & Probabilty – A punnet square shows all the possible allele combinations
from theparents of an organism. Punnett squares can help determine the probability of a gene
trait. Probability is the mathematical chance that an event will occur.
12. Sex Chromosomes – Sexchromosomes carry genes that determine whether or not an
organism is male or female. The female chromosome is displayed with an X, and the male
with a Y. The egg always contains the female chromosome. The sperm cells have an equal
mix, some Y some X. If a sperm cell with a Y chromosome fertilizes and egg the offspring
will be male. If a sperm cell with an X chromosome fertilizes an egg the offspring will be
female. (226)
13. Incomplete Dominance – Sometimes one allele isn’t completely dominant over another allele.
In this case the phenotypes (appearance) of the alleles blend. This is called incomplete
dominance. This happens when 2 dominant genes combine. Example: A white flower and
a red flower produce pink flowers. (227)
14. Codominance – In codominance both the phenotypes of the gene are displayed at the same
time. Example: A black cat and a tan cat produce offspring that are black and tan. (227)
15. Polygeneic Traits – Traits that are determined by more than one set of genes are called
polygenic. Feather color in parakeets is a good example. Skin tone and eye color in humans
is determined by 4 sets of genes. (228)
16. DNA – Chromosomes consist of molecules of DNA. These are arranged in sections we call
Genes. Genes determine traits. (238)
17. Double Helix - DNA is shaped like a twisted ladder. This is called a double helix. The sides
of the ladder consist of alternating sugar and phosphate molecules. The rungs of the ladder are
composed of chemical building blocks called bases. There are four of them: Adenine (A),
Thymine (T), Cytosine (C), and Guanine (G). (238)
18. DNA Replication – When DNA molecules make an exact copy of themselves this is called
DNA replication. During replication adenine (A) combines only with thymine (T), and
cytosine (C) combines only with guanine (G). This way the DNA makes 2 exact copies of
itself (daughter molecules). We will go over this in class.(239)
19. Base Sequences & Protein Synthesis –The order of base pairings in a DNA gene is called
the base sequence. These base pairings along the genes determine the production of various
proteins. The production of these proteins is called protein synthesis.
Note: Proteins are made from long chains of molecules called amino acids. (240)
20. Mutation – A change in the hereditary material of an organism is called a mutation. (242)
21. Genetic Disorder – An abnormal condition that an organism inherits from its parents is called
a genetic disorder (cystic fibrosis, hemophilia, sickle cell anemia, downs syndrome). (243)
22. Selective Breeding – The process of selecting organisms with desired traits to serve as parents
for the next generation is called selective breeding. (245)
23. Genetic Engineering – The process of transferring genes from one organism into the DNA of
another organism is called genetic engineering. (246)
24. DNA Fingerprinting – The process of producing an image of patterns from someone’s DNA
Is called DNA fingerprinting. ( 247)
25. Genome – A genome is the total amount of hereditary material in a single cell of am
organism. (248)
26. Mitochondrial DNA – Mitochondrial DNA is found outside of the nucleus in themitochondria of
the cell. It is inherited only from the mother because it is only found in the egg cell. (248)