Chapter 8 inheritance, genes and chromosomes
Terms in this set (72)
Observable physical feature, such as seed and shape
Particular form of character such as wrinkled or smooth peas
Offspring of crosses between organisms differing in one or more characters
2copies of each gene
Different form of same gene
2alleges that are the same
2 diff alleles
Law of segregation
When any individual produces gametes
Law of independent assortment
Alles of different genes assort independently of one another during gametes formation
Rare, stable, an inherited change of genetic material
Present in most individual in the nature
Two alleles that share or "combine" giving a phenotype that is unlike but similar to either parent.
2 alleles of a gene both produce their phenotype when presented in heterozygote
Phenotype expression of one gene is affected by another gene
(Heterosis) The quality of hybrids to have quantitative traits that are greater than either parent resultant from the interaction of different alleles of several genes.
Traits conferred by multiple genes need to be measure rather than qualitative
Portion of individual in a group with given genotype that actually show the expected phenotype
Is the degree to wich a genotype is expressed in an individual
The genetic basis of character; a piece of DNA that contains information regarding a phenotype of a trait
The generation that donates the original ancestry traced for a particular trait from the egg or sperm or pollen and pistol.
first (F1) Generation
The resultant organism and its traits from the crossing of the parental generation.
Second (f2) Generation
The resultant organism and its traits from crossing of F1 individuals.
The crossing of 2 parents differing in only one trait
The crossing of 2 parents differing in two traits
The trait that is 100% present in the F1 generation.
The trait that disappears in the F1 generation but reappears in the F2 generation.
One copy of the organism set of chromosome
2 copies of the organism set of chromosome
2 copies of a gene in a diploid organism are the alleles, the same version of a gene
The two copies of a gene in a diploid organism are different alleles, different versions of the gene.
A tool to used to show how genes segregate in successive generations
A phylogenetic tree or genealogy showing the generations of a family lineage in regards to a certain trait or disease and the sex and relatedness of individuals for that trait or disease.
A change in phenotype resulting from a change in DNA sequence. A phenotype or allele that is found less than 1% of the time.
Any allele of a gene is that found anywhere between 1% and 99% of the time and expresses the most common phenotype.
A variant of an allele that is expressed somewhere between 1% and 99% of the time.
hierarchy of dominance
Different alleles of a gene have differing dominant forms such as one is completely dominant, one is completely recessive and other show degrees of dominance that are more or less than the other alleles.
One gene has dominance over another gene, such that the first gene controls the phenotypic expression of the second gene.
a cross between two true breeding parents for one or more traits
These are traits that cannot be measured individually, but must be measured with quantitative measurements such as the amount of corn produced per acre of farmland
position on a chromosome where gene is located
gene phenotypes are always inherited together, they are on the same chromes
Chromosome sets where each sister chromosome is identical
chromosome sets where in some portion of the population the 2 chromosome are different
and individual where at least one chromosomal pair are not identical chromosomes
Sex linked Inheritance
Genes that are on sex chromosomes where individuals hemizygous for a recessive trait will express it because there is no corresponding chromosome to to fill in for a defective trait. An example is hemophilia in the royal families of Europe.
Lateral(Horizontal) Gene Tranfer
In bacterial conjugation, the transfer of genetic material as pieces of DNA or plasmids, from one bacteria to another.
a small self-replicating chromosome in bacteria that can be passed to other bacteria through bacterial conjugation. An example would be transference of a gene on a plasmid that gives antibiotic resistance that was in one bacteria to another.
A thin projection (tube) through which transfer of genetic material from donor to recipient bacteria takes place.
The transfer of DNA from a donor bacteria to a recipient bacteria.
1. How are characteristics and traits related?
a. Characteristics are things general traits like eye color, hair color, skin color, ear lobe, etc.
b. Traits are variations of characteristics: E.g., brown, black or blond hair.
2. What are Mendel's Laws of Genetics? How many are there? Explain them. How does what we learned about cell division help us understand these laws?
a. Law of Segregation: There are two copies of a gene that separate (segregate) from each other during gamete formation. There are two copies of each gene in a cell on two sister chromosomes (diploidy). During Meiosis, these separate into haploid gametes which contain only one copy of each gene.
b. Law of Independent Assortment: Individual genes sort separately from each other into their respective gametes. During Cell division, chromosomes are randomly drawn to one side or the other during anaphase which means that any gamete can have a chromosome containing different combinations of alleles of different genes.
3. What is a test cross? How does it work?
a. A test cross check to determine the genotype of an individual for one character.
b. It works by crossing the individual with another individual that is homozygous recessive for that trait. If the offpring come out all with a dominant trait, the individual being tested in homozygous dominant. If the percentage is 50% Dominant/50% recessive, the individual is heterozygous for that gene.
4. What is the result of a monohybrid cross between two heterozygotes?
a. 75% Dominant, 25% recessive with 25% being homozygous dominant, 50% being heterozygotes, and 25% being homozygous recessive.
5. What is the result of a monohybrid cross between a homozygous recessive and a homozygous dominant individual?
a. 100% Dominant phenotype with all being heterozygotes
6. What is the result of a dihybrid cross between two individuals heterozygous for both genes?
a. 9 Dominant for both genes, 3 Dominant for the first gene/recessive for the second gene, 3 recessive for the first gene/dominant for the second gene, 1 recessive for both genes.
7. What is the result of a dihybrid cross between a individual homozygous recessive for both genes and a homozygous dominant individual for both genes?
100% heterozyous for both genes
8. What characteristics are observed in a pedigree (phylogenetic tree or genealogy) for a dominant trait?
a. It appears in all generations
b. Somewhere between all to half of the offspring will be affected
9. What characteristics are observed in a pedigree (phylogenetic tree or genealogy) for a recessive trait?
a. Affected individuals usually do not have an affected parent
b. Only a small proportion of the individuals in the tree will be affected.
10. What characteristics are observed in a pedigree (phylogenetic tree or genealogy) for a sex-linked trait?
a. Usually only shows up in hemizygous individuals (males in the case of humans)
b. Mothers are carriers but do not express
c. If mother is carrier, there is 50% chance her sons will have it
11. What is thought to be the reason for hybrid vigor?
a. The combination of two different alleles creates more vigorous offspring
12. Give examples of codominance, hierarchy of dominance, and incomplete dominance?
a. Codominance: Blood Types
b. Hierarchy of Dominance: rabbit coat color - black > chinchilla > Point restricted > albino
c. Incomplete Dominance: Snapdragons, red flowered parent crossed with a white flowered parents gives pink flowered offspring
13. Why does the fact that type AB blood is the universal acceptor blood type tell us about codominance?
a. It shows us that both the A surface protein on white blood cells and the B surface protein can exist together and not have one be repressive of the other.
14. Why do some genes sort independently while others do not?
a. Linked genes are on the same chromosome and sort together.
b. Independently assorted genes are on different chromosomes
15. Explain how one can determine the relative position of genes on a chromosome by their recombinant frequencies.
a. The closer that two genes are together on a chromosome the less chance there is that they will be divided between two different chromosomes during homologous recombination during Meiosis I.
b. By comparing the amount of times one sees Linked phenotypic traits in parents diverge into different linked phenotypes in offspring, one can determine if the genes are closer or farther apart on the chromosome.
c. The farther apart the two genes are the more likely that the linked traits will diverge. The closer the genes are, the less likely it is the traits will separate from each other.
d. By making comparisons of these divergences and drawing a map one can get the relative order of the genes on the chromosome.
16. Why do males usually express the phenotype of sex-linked characteristics more than females?
a. Males do not have an extra copy of the X chromosome to offset the effects of the defective protein.
17. Explain how and why cytoplasmic (maternal) inheritance occurs.
a. Cytoplasmic inheritance occurs because a trait is carried by a gene on mitochondrial or chloroplast genome which is primarily passed on through the gametes of the female.
18. Explain how lateral gene transfer occurs and how this process can increase antibiotic resistance in bacteria.
a. Lateral transfer is the passing of genetic information through the sex pilus of a donor bacteria to a recipient bacteria.
b. Lateral transfer passes pieces of DNA containing genes that can become incorporated into the genome of the recipient bacteria or plasmids with genes which can start replicating in the donor bacteria.
c. Bacteria that are resistant to an antibiotic through the function of a protein encoded by a gene on a plasmid or piece of DNA transferred through the sex pilus, will confer the antibiotic resistance to the recipient bacteria.