Genetics: Chromosomes and Traits
32 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of a chromosome in an organism?

A chromosome serves as a DNA molecule that contains part or all of the genetic material of an organism.

How does a sister chromatid differ from a homologous chromosome?

A sister chromatid is an identical copy of a single chromosome connected by a centromere, while a homologous chromosome is a pair of chromosomes from each parent that are similar but not identical.

Define the terms locus, gene, and allele, and explain their relationships.

A locus is a specific location on a chromosome, a gene is a DNA sequence coding for a trait, and an allele is a variation of a gene found at a locus.

Why can't all traits be represented in a Punnett square?

<p>Not all traits can be modeled with a Punnett square because it is designed for simple Mendelian traits, while complex or polygenic traits cannot be accurately depicted.</p> Signup and view all the answers

What is a lethal allele and how does it affect genetic cross results?

<p>A lethal allele is one that causes the death of an organism, influencing genetic cross results by skewing expected ratios of offspring.</p> Signup and view all the answers

Describe the processes by which sex is determined in animals.

<p>In many animals, sex is determined by sex chromosomes, like the XY system in humans, while in others, environmental factors can play a role.</p> Signup and view all the answers

Give an example of a polygenic trait and explain why it cannot be accurately predicted by a Punnett square.

<p>Height is a polygenic trait influenced by multiple genes, making it complex and unsuitable for prediction with a Punnett square.</p> Signup and view all the answers

How do the characteristics of homologous chromosomes assist in genetic diversity?

<p>Homologous chromosomes carry genes in the same order but may have different alleles, contributing to genetic variation when inherited from each parent.</p> Signup and view all the answers

What is temperature-dependent sex determination, and which group of animals exhibits this trait?

<p>Temperature-dependent sex determination is a phenomenon where the sex of an organism is determined by the temperature during a critical period of development, seen in some reptiles.</p> Signup and view all the answers

How do X-linked traits differ in their inheritance patterns compared to autosomal traits?

<p>X-linked traits are more commonly expressed in males due to them having only one X chromosome, while autosomal traits do not show such sex-based inheritance.</p> Signup and view all the answers

Contrast haploid and diploid cells, and explain how each type is produced.

<p>Haploid cells have one set of chromosomes (n) and are produced by meiosis, while diploid cells have two sets (2n) and are produced by mitosis.</p> Signup and view all the answers

What does incomplete penetrance mean, and what might cause it?

<p>Incomplete penetrance refers to situations where not all individuals with a dominant allele express the expected phenotype, often due to environmental factors or gene interactions.</p> Signup and view all the answers

How many alleles of a single gene can exist in a given population, and how many can a diploid individual possess?

<p>A population can possess many alleles of a single gene due to genetic diversity, while a diploid individual carries only two alleles for that gene.</p> Signup and view all the answers

Define polygenic traits and provide an example, along with some challenges in their study.

<p>Polygenic traits are influenced by multiple genes, resulting in continuous variation; an example is human height. Challenges include the interaction of numerous genes, environmental impacts, and difficulty isolating specific gene effects.</p> Signup and view all the answers

What is the XO chromosomal system, and in which organisms is it typically found?

<p>The XO chromosomal system involves females having one X chromosome (XO) and males having two (XX), and it is typically found in some insects, such as grasshoppers.</p> Signup and view all the answers

Explain how sex determination in clownfish is influenced by social hierarchy.

<p>In clownfish, social hierarchy can lead to sex change, where dominant females can change their sex to male if the male partner is removed or absent.</p> Signup and view all the answers

Males in the XY chromosome system have two X chromosomes.

<p>False</p> Signup and view all the answers

All organisms exist primarily in a diploid stage.

<p>False</p> Signup and view all the answers

Incomplete penetrance means that every individual with a dominant allele will express the trait.

<p>False</p> Signup and view all the answers

A diploid individual can carry two alleles of a single gene, one from each parent.

<p>True</p> Signup and view all the answers

Environmental factors have no effect on the expression of X-linked traits.

<p>False</p> Signup and view all the answers

Polygenic traits only involve a single gene and show distinct categories of variation.

<p>False</p> Signup and view all the answers

Temperature-dependent sex determination occurs in some reptiles.

<p>True</p> Signup and view all the answers

Haploid cells are produced through mitosis.

<p>False</p> Signup and view all the answers

Humans have 46 chromosomes that come in 23 pairs.

<p>True</p> Signup and view all the answers

A homologous chromosome is an identical copy of another chromosome.

<p>False</p> Signup and view all the answers

A Punnett square can be used to predict the outcomes of any genetically inherited traits.

<p>False</p> Signup and view all the answers

In reptiles, sex determination can be influenced by temperature factors.

<p>True</p> Signup and view all the answers

Lethal alleles can only affect individuals in the homozygous form.

<p>False</p> Signup and view all the answers

An allele is a specific location on a chromosome where a gene is found.

<p>False</p> Signup and view all the answers

Complex traits, such as height, can be represented accurately using a Punnett square.

<p>False</p> Signup and view all the answers

Sister chromatids are formed during DNA replication and are identical copies of a chromosome.

<p>True</p> Signup and view all the answers

Study Notes

Chromosome, Sister Chromatid, and Homologous Chromosome

  • Chromosome: A DNA molecule containing an organism's genetic material. Humans have 46 chromosomes in 23 pairs.
  • Sister Chromatid: Two identical copies of a single chromosome, connected by a centromere, created during DNA replication.
  • Homologous Chromosome: Chromosomes similar in size, shape, and genetic content, one inherited from each parent. They share the same genes but may have different alleles.

Locus, Gene, and Allele

  • Locus: A specific location on a chromosome where a gene is found.
  • Gene: A DNA sequence that codes for a protein and determines a trait. Each gene has a specific locus.
  • Allele: Different versions of a gene at a given locus. For example, eye color genes have alleles for blue or brown eyes.

Punnett Squares and Traits

  • Punnett squares are best for simple Mendelian traits (one gene, two alleles).
  • Complex traits (e.g., polygenic, environmental influences) cannot be accurately predicted using Punnett squares.
  • Examples of traits that can be represented by Punnett squares are blood types (ABO). Height and skin color, however, are polygenic traits.

Lethal Alleles

  • Lethal Allele: An allele causing an organism's death, often early in development (homozygous or heterozygous).
  • Impact on Genetic Crosses: Lethal alleles skew expected ratios in genetic crosses. For example, if a recessive condition is lethal, only heterozygous and homozygous dominant individuals survive.

Sex Determination

  • Methods of Sex Determination: Sex in animals varies with environmental, social, or chromosomal factors.
  • Environmental Factors: Temperature (reptiles) or social status (certain fish).
  • Chromosomal Factors (XY System): Males have XY; females have XX chromosomes—common in mammals.
  • Chromosomal Factors (ZW System): Males have ZZ; females have ZW chromosomes—common in birds, some reptiles, and some fish.
  • Chromosomal Factors (XO System): Females have XO; males have XX chromosomes—common in some insects like grasshoppers.

X-linked Inheritance

  • X-linked Inheritance: Genes located on the X chromosome.
  • Difference from Autosomal Genes: X-linked traits show different inheritance patterns, often affecting males more frequently. Autosomal genes are not sex-linked.

Haploid and Diploid Cells

  • Haploid (n): Cells with one set of chromosomes (gametes).
  • Diploid (2n): Cells with two sets of chromosomes, one from each parent (body cells).
  • Production Methods: Haploid cells are produced by meiosis; diploid cells are produced by mitosis.
  • Presence in Organisms: Not all organisms have both. Many plants and some fungi alternate between haploid and diploid phases; animals are primarily diploid.

Incomplete Penetrance

  • Incomplete Penetrance: Not all individuals with a dominant allele express the trait.
  • Reasons: Environmental factors, interactions with other genes, or developmental processes.

Alleles in Populations and Individuals

  • Population Alleles: Many alleles of a single gene can exist in a population.
  • Diploid Individual Alleles: A diploid individual has only two alleles for a given gene.

Polygenic Traits

  • Polygenic Trait: Traits influenced by multiple genes.
  • Examples: Human height, skin color.
  • Challenges: Studying polygenic traits is complex due to multiple genes, environmental factors, and isolating individual gene effects.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Description

This quiz covers key concepts in genetics, focusing on chromosomes, sister chromatids, homologous chromosomes, genes, alleles, and Punnett squares. Test your understanding of how these genetic elements interact and influence traits. Ideal for students studying introductory genetics.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser