Mendelian Genetics and Inheritance Patterns

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Questions and Answers

What key observation from Mendel's pea plant experiments disproved the blending theory of inheritance?

The lack of variation in the initial pure strains.

The large number of plants grown in the experiments.

The presence of 7 different characteristics in the plants.

The consistent 3:1 ratio of phenotypes in the second generation. (correct)

Which term best describes a specific physical location of a gene on a chromosome?

Genotype

Phenotype

Locus (correct)

Allele

What is the difference between a monogenic trait and a polygenic trait?

Monogenic traits are discrete, while polygenic traits are continuous. (correct)

Monogenic traits are visible, while polygenic traits are not visible.

Monogenic traits are influenced by many genes, while polygenic traits are influenced by a single gene.

Monogenic traits are always recessive, while polygenic traits are always dominant.

What cellular process specifically produces gametes?

Meiosis (C) Signup and view all the answers

Approximately what percentage of human DNA directly codes for proteins?

2-3% (A) Signup and view all the answers

What change best describes an epigenetic modification?

A change in DNA structure that affects gene expression without altering the base sequence (A) Signup and view all the answers

What does it mean for a gene to exhibit polymorphism?

The gene has two or more alleles at a locus, leading to different genotypes. (A) Signup and view all the answers

How many chromosomes are typically found in a human somatic cell?

46 (D) Signup and view all the answers

Which component is NOT part of the DNA double helix backbone?

Nitrogenous base (D) Signup and view all the answers

What is the primary function of a codon?

To code for a specific amino acid (C) Signup and view all the answers

Which statement best describes the role of homeobox (Hox) genes?

They act as regulatory genes during development. (C) Signup and view all the answers

What is the result of a mutation in the coding region of a gene?

An alteration in the structure and function of proteins produced. (C) Signup and view all the answers

What is meant by a neutral mutation?

A mutation that is neither advantageous nor deleterious to an organism (D) Signup and view all the answers

Which of the following is NOT a force of evolution?

Gel electrophoresis (C) Signup and view all the answers

What is the relationship between codon sequences and protein structure?

Codon sequences determine the amino acid sequence, which dictates protein structure. (A) Signup and view all the answers

Which agricultural practice is directly associated with the farming methods described in the text?

Slash and burn (B) Signup and view all the answers

What does 'polymorphic' refer to in the context of protein-producing loci?

A locus in which a gene has multiple forms. (D) Signup and view all the answers

If a person has the genotype AS, what condition do they possess?

Sickle cell trait (B) Signup and view all the answers

Which organism is responsible for transmitting Plasmodium falciparum?

Anopheles mosquito (C) Signup and view all the answers

Where does uncontrolled reproduction of Plasmodium falciparum primarily occur within the human body?

Red blood cells (D) Signup and view all the answers

What is the key consequence of the genetic mutation related to sickle cell anemia?

Change in a single DNA base leading to a change in an amino acid (D) Signup and view all the answers

In the context of genetic inheritance, what is indicated by the term 'codominance'?

Both alleles are expressed simultaneously in the heterozygote (C) Signup and view all the answers

According to the content, what type of selection is described when both homozygotes are fitter than the heterozygotes?

Disruptive selection (D) Signup and view all the answers

What does the term 'higher chance of survival and reproducing' imply in the context of natural selection?

Greater adaptation to the environment (D) Signup and view all the answers

What is the effect of gene flow on genetic variation within a breeding population?

It increases genetic diversity by introducing new individuals from outside populations. (C) Signup and view all the answers

In the context of natural selection, what is a crucial condition that must be met?

There must be a stress resulting in differential mortality between groups of individuals. (D) Signup and view all the answers

What was the main environmental stressor that led to directional selection in the medium ground finch population studied by Peter and Rosemary Grant in 1977?

A decrease in rainfall, leading to a food shortage of small seeds. (B) Signup and view all the answers

In the case of the medium ground finch, what was the primary factor that led to the increase in average body size in the generation following the 1977 drought?

The survival of larger birds with stronger beaks during this drought. (D) Signup and view all the answers

What was the effect of the return to normal rainfall levels on the average body size of the medium ground finch?

The average body size gradually decreased until 1983. (C) Signup and view all the answers

What effect did the El Nino event have on the medium ground finches?

It resulted in flooding, favoring smaller birds. (A) Signup and view all the answers

What is a monogenic trait?

A trait that is determined by a single gene. (C) Signup and view all the answers

What was the primary cause of the increased survival rate of dark-colored peppered moths during the industrial revolution?

The increased pollution that darkened the tree trunks. (B) Signup and view all the answers

What is the key characteristic of stabilizing selection for monogenic traits?

It maintains a balanced polymorphism where the heterozygote has a survival advantage. (C) Signup and view all the answers

What is true about the sickle cell allele (S) in populations where malaria is endemic?

The S allele is beneficial through heterozygote advantage. (B) Signup and view all the answers

Who were mainly affected by malaria, causing a natural selection for the sickle cell allele?

Bantu horticulturists who lived in sedentary settlements. (D) Signup and view all the answers

Before 1500-2000 years before present, what was the status of malaria in Africa?

It was minimal due to small mobile populations of hunter and gatherers. (B) Signup and view all the answers

What is the difference in probability of survival between the dark peppered moth and the light peppered moth, during the industrial revolution?

The dark peppered moths had a 15% greater chance of survival. (C) Signup and view all the answers

Which of these options are correct? (Select all that apply)

Directional selection can result in substantial genetic change in a short period of time (B), Stabilizing selection for polygenic traits favors average phenotypes with less variation (D) Signup and view all the answers

Study Notes

Mendel's Experiments

Gregor Mendel (1822-1884) conducted breeding experiments on pea plants.
He used 28,000 plants and 400,000 seeds.
Mendel's experiments disproved the blending theory of inheritance.
He demonstrated discrete units of inheritance (genes) that maintain their identity when passed from parents to offspring.

Inheritance Patterns

No Blending: Inheritance occurs through discrete units, not blending.
Dominance/Recessiveness/Codominance: Different forms of a gene (alleles) can exhibit dominance, recessiveness, or codominance.
Locus: The physical location of a gene on a chromosome.
Alleles: Different forms of the same gene.
Homozygotes: Individuals with two identical alleles for a gene.
Heterozygotes: Individuals with two different alleles for a gene.
Genotype: The genetic makeup of an individual (combination of alleles).
Phenotype: The observable physical traits resulting from the genotype.
Monogenic Traits: Traits controlled by a single gene, and are discrete (e.g., pea shape).
Polygenic Traits: Traits controlled by multiple genes, and are continuous (e.g., human height).
Polymorphism: The existence of two or more alleles at a single locus.

Chromosomes

Chromosomes are containers of DNA.
Humans have 23 pairs of chromosomes (46 total), one from each parent.

DNA

Structure: DNA is a two-stranded double helix. The backbone is composed of phosphates and sugars (deoxyribose), and rungs (base pairs) are formed by bases (adenine, thymine, cytosine, and guanine).
Function: Genes (coding sequences within DNA) produce proteins.
Junk DNA Controversy: The portion of DNA previously considered non-coding now shows it has regulatory genes.
Non-coding RNA: RNA molecules that participate in gene regulation, also found in non-coding portions of DNA.

Epigenetics

Changes in DNA structure without altering the base sequence.
Methylation and responses to the environment can affect gene expression.

Genes and Proteins

Genes produce proteins.
More than 100,000 proteins can be produced by human genes at the minimum.

Meiosis

Cell division in germ cells (sperm and egg).
Creates gametes with half the number of chromosomes as parent cells

Evolution

Mutations: ultimate source of genetic variation.
Gene flow: Movement of individuals between populations leading to genetic exchange. Increases genetic diversity within the receiving population, reducing it between populations.
Natural selection: Differences in survival and reproduction among individuals, leading to changes in allele frequencies.

Directional Selection and Polygenic Traits

Directional selection: The environment selects individuals who are best adapted to those stresses, favoring a specific trait variation over existing trait variation.
Polygenic traits: Traits influenced by multiple genes, such as size and weight in finches, exhibiting continuous variation. The fittest have intermediate traits.
Natural selection: In stressful environments, some traits are advantageous.

Monogenic Traits and Stabilizing Selection (Discontinuous Variation)

Monogenic traits: Characteristics affected by a single gene.
Stabilizing selection: Environment favors average traits (stabilized phenotype); the extremes are not as suited for survival. Example: moth color changing in pollution environment
Balance polymorphism: Multiple traits maintaining in a population that maintain balance (neutral or beneficial).

Sickle-Cell Anemia

Genetic disorder affecting hemoglobin (protein for oxygen transport in blood).
Individuals with one sickle cell allele (AS) tend to have higher fitness in malaria-prone areas compared to those without the allele or with two sickle cell alleles (SS).
The balance of sickle cell allele with normal allele is a form of balanced polymorphism.

Codominance

More than one allele influences a phenotype.
For sickle cell, homozygotes (SS) have sickle cell anemia (negative phenotype) and the heterozygotes (AS show a mixed phenotype (trait).

Microevolution

Study of evolution over observable periods of time.
Focuses on changes within a population and how allele variations are passed on.

Macroevolution

Studying evolution over a very long time, which is not directly observable in a human lifetime.

Population Genetics

Study of genetic variation within populations.
The units of evolution are breeding populations.

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Description

Explore the foundational concepts of Mendelian genetics through Gregor Mendel's experiments with pea plants. This quiz covers key principles including dominance, recessiveness, and the nature of alleles. Test your understanding of how inheritance patterns shape the traits of living organisms.