Chapter 7: Extending Mendelian Genetics - Flashcards

Flashcards for reviewing Chapter 7: Extending Mendelian Genetics.

What determines an organism's sex?

Sex chromosomes

What are chromosomes that do not directly affect an organism’s sex called?

Autosomes

Does a carrier show symptoms of a genetic disorder?

No

Can a carrier pass a genetic disorder to offspring?

Yes

Where are sex-linked genes located?

On the sex chromosomes (X and Y)

In humans, what determines the sex of the offspring?

A gamete from a male

What chromosomes can a male pass on?

Either X or Y chromosomes

What chromosomes can a female pass on?

Only X chromosomes

What are the genes on the Y chromosome responsible for?

Male characteristics

In whom does X chromosome inactivation occur?

Females

Where does X chromosome inactivation occur?

One of the two X chromosomes in every cell is randomly turned off

Carrier

A person who "transports" a disease-causing allele to offspring

Incomplete Dominance

Neither allele is completely dominant, with the heterozygous phenotype being somewhere between the homozygous phenotypes.

Codominance

Both alleles are completely expressed.

Multiple-allele trait

The gene has more than two alleles.

Polygenic traits

Produced by two or more genes and show a continuous range of phenotypes.

Epistasis

One gene affecting the expression of other genes involved in a particular trait.

What can affect gene expression?

Environment

Incomplete dominance

Neither allele is dominant

Codominance

Both alleles are expressed together

Polygenic

Traits that are produced by two or more genes

Gene linkage

Genes that are on the same chromosome and tend to be inherited together.

What was useful in Morgan’s research?

Fruit flies

Wild type

The most common phenotype

Mutant type

A less common phenotype

Linkage maps

Distance estimates between genes.

What do linkage maps estimate?

Distances between genes

What did Morgan conclude from his fruit fly research?

Linked genes are on the same chromosome, chromosomes (not genes) assort independently during meiosis, and homologous genes can be exchanged through crossing over during meiosis.

What is the likelihood of genes inherited together as distance decreases?

More likely

What is the likelihood of genes inherited together as distance increases?

Less likely

Linkage map

A map of the relative locations of genes on a chromosome.

Linkage map

Crossover frequencies relate to map linkages

What do linkage maps show about genes on a chromosome?

An estimate of physical distance between genes and the relative locations of genes.

In what organisms does genetic inheritance follow similar patterns?

All sexually reproducing organisms

What is the inheritance of single-gene traits?

Straight-forward

What can females carry?

Sex-linked genetic disorders

What can carry autosomal disorder?

Both males and females

Males and sex-linked genetic disorders

Males are never carriers

Pedigree

A chart that traces phenotypes and genes in a family.

In pedigree analysis, what is used to infer the genotype?

Phenotype

If approximately the same number of males and females show the phenotype in a pedigree, the gene is most likely on what?

Autosome

What do karyotype and pedigrees help study?

Human chromosomes

Karyotype

Photograph

Sex chromosomes

Determine an organism's sex

Patterns of expression for autosomal genes

Two copies of each autosome which leads to two copies of each autosomal gene. Both copies of a gene can affect phenotype.

Carrier

People who have one dominant allele and one recessive, disorder-causing allele, do not have the disorder, but can pass it on because they are carriers of the disorder.

Sex-linked genes

Genes on the sex-chromosomes (the X and Y chromosomes in many species).

Patterns of expression for sex-linked genes

Males have only one copy of each sex chromosome, all of the genes on each chromosome will be expressed. Expression of sex-linked genes in females is similar to the expression of autosomal genes: two copies of each gene can affect phenotype. One X chromosome in each cell is randomly turned off by a process called X chromosome inactivation.

Incomplete dominance

Neither of two alleles is completely dominant or completely recessive. Instead, the alleles show incomplete dominance, where the heterozygous phenotype is somewhere between the homozygous dominant and homozygous recessive phenotypes. The heterozygous phenotype is a third, distinct phenotype.

Codominance

Two alleles of a gene are completely and separately expressed, and both phenotypes are also completely expressed.

Polygenic traits

Traits that are produced by two or more genes.

Epistasis

An epistatic gene is a gene that can affect the expression of all of the other genes that affect a trait.

Ways genotype and the environment can interact

Temperature affects sex determination of sea turtles + Human height

Mendel's law of independent assortment - inaccurate

Some genes were linked together and did not assort independently.

Relationship between the distance between two genes and the chance that they will be inherited together

If two genes are close together, it is very likely that they will be inherited together. If two genes are far apart, it is much more likely that they will be separated by the crossing over that occurs during meiosis.

Linkage map

A map of the relative locations of genes on a chromosome.

Distances between genes determined for a linkage map

By finding the percentage of times that cross-overs occur from observations of phenotypes in offspring, it is possible to make a map of the locations of the genes

Why can only females be carriers of sex-linked disorders?

Females, who have an XX genotype for their sex chromosomes, must have two recessive alleles to show a recessive phenotype, such as for a recessive sex-linked disorder.

Pedigree

A chart that is used to trace phenotypes and genotypes within a family

Difference in pedigrees between autosomal and sex-linked genes

Equal numbers of males and females will have the recessive phenotype. More males than females will have the recessive phenotype.

What determines the most traits expressed in a person’s phenotype?

Autosomal genes

Where does X chromosome inactivation occur?

cells of female mammals

Dominance and recessiveness

Most traits are produced by genes with multiple alleles.

What are eye color, hair color, and skin color considered?

Polygenic traits

What is evidence that phenotype differences happen?

Environment and genotype interact to affect phenotype.

Linked genes - Thomas Hunt Morgan’s research

Located on the same chromosome.

Inherited genes

Two genes on a given chromosome that are most likely to be inherited together are 2 map units apart.

The chart that traces the phenotypes and genotypes within a family

Pedigree

A genetic disorder traced within a family that occurs mostly in males

The gene for this disorder is most likely on the X chromosome

Karyotype

Large changes in chromosomes

Disorder caused by recessive allele

Homozygous for the recessive allele

Gene expression

Environment

What is the chance any of their children will inherit the disorder? (dominant GG allele)

75%

XX female to express a recessive sex-linked trait

must have two recessive alleles.

What are polygenic traits affected by?

The interaction of several genes,

Carrier

Does not have the disorder, but can pass it on

What sex is most often observed in sex-linked disorders?

Males + The Y chromosome cannot mask alleles on the X chromosome.

Match up chromosome pairs.

Karyotype

Parental Generation- Red x White Pea Plants

C1C1 and C2C2

First generation-unlabeled pea plant phenotype

Pink flowers

Pea plant allele interaction for flower color

Incomplete Dominance

what relationship in pea plant flower colors would show partly red and partly white.

Codominance

What diagram is used in figure 7.4?

Pedigree Chart

If a phenotype is caused by a dominant allele, what is it in Figure 7.4?

One parent has the phenotype and at least one offspring does not have the phenotype and there are approximately equal numbers of males and females with the phenotype.