Transmission Genetics Oral Exam 1

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Questions and Answers

What is a characteristic of the XY sex determination system?

Females have XY chromosomes

Females have ZW chromosomes

Males have XY chromosomes (correct)

Males have XX chromosomes

Which sex determination system is characterized by females developing from unfertilized eggs?

XO system

ZW system

XY system

Haplodiploidy (correct)

How do hormonal influences affect sex determination?

They are irrelevant in sex differentiation.

They only affect genetic mutations.

They play a role during critical periods of development. (correct)

They primarily determine temperature effects.

What temperature effect is associated with sex determination in some reptiles?

Warmer temperatures usually result in female development. Signup and view all the answers

What effect can mutations in the SRY gene have on sex development?

They can result in XY individuals developing as females. Signup and view all the answers

Which of the following correctly describes a sister chromatid?

Two identical copies of a single chromosome connected by a centromere. Signup and view all the answers

What is the relationship between a locus, a gene, and an allele?

A gene is a sequence of DNA that codes for a trait and has a specific locus. Signup and view all the answers

What is a polygenic trait?

A trait influenced by multiple genes. Signup and view all the answers

Which of these traits can be accurately predicted using a Punnett square?

Blood type determination. Signup and view all the answers

What distinguishes sister chromatids from homologous chromosomes?

Sister chromatids are identical copies of a chromosome, while homologous chromosomes are not. Signup and view all the answers

What is defined as a lethal allele?

An allele that causes the death of an organism. Signup and view all the answers

How do lethal alleles affect the results of genetic crosses?

They can skew expected Mendelian ratios by preventing certain genotypes from surviving. Signup and view all the answers

Which statement about alleles is true?

Alleles represent variant forms of a gene. Signup and view all the answers

What is a locus in genetics?

The specific location of a gene on a chromosome. Signup and view all the answers

In humans, how is sex typically determined?

By specific paired sex chromosomes, such as the XY system. Signup and view all the answers

What influence does temperature have on sex determination in certain reptiles?

It can influence whether the reptile is male or female. Signup and view all the answers

Which of the following is a challenge in studying polygenic traits?

Environmental influences that affect trait expression. Signup and view all the answers

Which of the following statements about homologous chromosomes is correct?

They carry the same genes in the same order, but can have different alleles. Signup and view all the answers

What is a significant factor that leads to males expressing X-linked recessive traits more often than females?

Males have only one X chromosome. Signup and view all the answers

What is the primary method through which haploid cells are produced in organisms?

Meiosis Signup and view all the answers

How many chromosomes do humans have?

46 chromosomes in total. Signup and view all the answers

Which of the following is NOT a reason why not all traits can be represented by a Punnett square?

All traits are determined by a single allele. Signup and view all the answers

What does incomplete penetrance indicate in genetic expression?

Some individuals with a dominant allele do not express the trait. Signup and view all the answers

During which phase of the cell cycle are sister chromatids formed?

S phase. Signup and view all the answers

What role do homologous chromosomes play in genetic diversity?

They can exchange genetic material during meiosis. Signup and view all the answers

How many alleles of a single gene can a diploid individual possess?

One allele from each parent, totaling two alleles. Signup and view all the answers

Which of the following traits is best described as polygenic?

Height influenced by multiple genes. Signup and view all the answers

In terms of chromosome sets, which statement is true regarding haploid and diploid cells?

Diploid cells contain two sets of chromosomes, while haploid cells contain one. Signup and view all the answers

Which of the following organisms typically does not have both haploid and diploid cells in its lifecycle?

Most animals Signup and view all the answers

What defines X-linked recessive inheritance in males?

A single recessive allele on the X chromosome results in expression of the trait. Signup and view all the answers

Which statement is true regarding X-linked dominant inheritance?

Females express the trait if they have at least one dominant allele. Signup and view all the answers

How do males inherit their X chromosomes in relation to X-linked traits?

From their mothers and pass it to all their daughters. Signup and view all the answers

What is a key difference in expression between X-linked recessive and autosomal recessive traits?

X-linked recessive traits are more commonly expressed in males. Signup and view all the answers

Which of these statements accurately reflects the carrier status for males and females in X-linked recessive traits?

Females can be carriers without expressing the trait. Signup and view all the answers

In which way are X-linked genes distinct from autosomal genes?

They are located on sex chromosomes rather than autosomes. Signup and view all the answers

Which characteristic distinguishes autosomal inheritance from X-linked inheritance?

Sex of the offspring does not affect the inheritance pattern of autosomal genes. Signup and view all the answers

How does the expression of X-linked dominant traits typically vary in males and females?

Males express them more severely due to their single X chromosome. Signup and view all the answers

What is the total number of chromosomes in human diploid cells?

46 Signup and view all the answers

Which process is responsible for producing genetically identical diploid daughter cells?

Mitosis Signup and view all the answers

Which statement correctly describes the role of meiosis?

It reduces the chromosome number by half to produce haploid cells. Signup and view all the answers

Which type of cells are typically involved in sexual reproduction?

Gametes Signup and view all the answers

In which organisms are haploid cells predominant during most of their life cycle?

Fungi and algae Signup and view all the answers

What does incomplete penetrance mean in genetics?

Not all individuals with a dominant allele express the trait. Signup and view all the answers

Which statement about haploid and diploid cells in animals is true?

Most animals have both haploid and diploid stages. Signup and view all the answers

Which statement is true concerning polydactyly and its inheritance?

It is an example of incomplete penetrance. Signup and view all the answers

Study Notes

Oral Exam 1 Questions (Transmission Genetics)

Distinguishing Terms:
- Chromosome: A DNA molecule containing the genetic material of an organism (humans have 46 in 23 pairs).
- Sister Chromatid: Two identical copies of a chromosome joined at the centromere, formed during DNA replication.
- Homologous Chromosome: Similar in size, shape, and genetic content; inherited from each parent but can have different alleles.
Relationship Between Locus, Gene, and Allele:
- Locus: Specific location on a chromosome where a gene is found.
- Gene: DNA sequence coding for a protein, determining a trait and having a specific locus.
- Allele: Different versions of a gene at a particular locus (e.g., blue or brown eyes).
Can Every Trait Be Represented by a Punnett Square?:
- No, not all traits.
- Punnett squares are best for simple Mendelian traits (controlled by one gene with two alleles).
- Complex traits (e.g., height, skin color) and those influenced by the environment cannot be accurately predicted.

Lethal Alleles

Lethal Allele: An allele causing the death of an organism, often early in development (can be homozygous or heterozygous).
Impact on Genetic Crosses: Lethal alleles can alter expected phenotypic ratios in genetic crosses.

Sex Determination in Animals

Sex Determination Factors:
- Genetic: XY system (humans), ZW system (birds)
- Environmental: Temperature (reptiles)
- Social (clownfish).

X-Linked Inheritance

X-linked Inheritance: Genes located on the X chromosome.
Differences from Autosomal Inheritance: X-linked traits often show different inheritance patterns, tending to be more common in males.

Haploid and Diploid Cells

Haploid (n): One set of chromosomes (gametes).
Diploid (2n): Two sets of chromosomes (most body cells).
Production: Haploid cells produced by meiosis; diploid cells by mitosis.
Organism Presence: Not all organisms have both haploid and diploid stages.

Incomplete Penetrance

Incomplete Penetrance: Not all individuals with a dominant allele express the associated phenotype.
Reasons: Environmental factors, interactions with other genes, random developmental processes.

Number of Alleles

Population: Many alleles for a single gene exist in a population due to genetic diversity.
Diploid Individual: A diploid individual carries two alleles per gene (one from each parent).

Polygenic Traits

Polygenic Trait: A trait influenced by multiple genes, resulting in continuous variation within a population (e.g., height, skin color).
Challenges: Studying polygenic traits is difficult due to the numerous genes involved, environmental influences, and complexities of isolating gene effects.

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Description

Test your understanding of key concepts in Transmission Genetics, including definitions of chromosomes, sister chromatids, and homologous chromosomes. Explore the relationships between locus, gene, and allele, and discover the limitations of Punnett squares in representing traits. Perfect for students preparing for oral exams!