2B2 Basic Principles of Genetics Flashcards
Understand how genetic information is passed and the mechanisms of inherited traits.
What is genetics?
The study of genes and DNA.
Who was Gregor Mendel and what was his contribution to genetics?
- He was a 19th-century Austrian monk and scientist.
- His research on the heredity of plants advanced the study of genetics.
He is often known as the ‘father of genetics’.
What organism did Mendel study to establish the foundations of genetics?
Pea plants.
What were some reasons Mendel chose pea plants for his experiments?
- Ease of growth.
- Controllable mating.
- Easily distinguishable features.
What are some examples of traits Mendel studied in pea plants?
- Flower color
- Pod shape
- Seed color
What did Mendel observe about the inheritance of traits in pea plants?
One trait often dominated or covered up another, leading to the description of dominant and recessive traits.
Who studied the concept of natural selection and its impact on genetic variation?
Charles Darwin
What is natural selection?
The process by which organisms better adapted to their environment tend to survive and produce more offspring.
What are inherited traits?
Traits passed down through generations due to DNA coding.
How do genetics and the environment influence traits like hair color?
Genetics provide the base color, while environmental factors like dyeing can change it temporarily.
What are chromosomes?
Linear segments of DNA containing many genes.
What are the two main types of chromosomes, and what distinguishes them?
- Sex chromosomes: contain genes for primary and secondary sex characteristics.
- Autosomes: contain genes for all other aspects of physiology.
What is a gene?
A section of DNA that codes for a particular protein.
What are structural genes and regulatory genes?
- Structural genes: code for proteins contributing to cell structure.
- Regulatory genes: control gene expression.
What are alleles?
Different versions of a gene that determine specific traits.
E.g. if the gene is eye colour, the alleles may be brown, blue, green, etc.
What is the genotype of an organism?
The combination of alleles an organism inherits for a particular gene.
What is the phenotype of an organism?
The observable traits of an organism e.g. fur colour.
How does a Punnett square help determine offspring genotypes?
It allows you to see the possible combinations of alleles from the parents, predicting the likelihood of certain traits appearing in the offspring.
Define a genome.
The complete set of genetic information in an organism.
What is the relationship between genotype and phenotype?
Genotype influences phenotype, but environmental factors can also play a role.
How does natural selection influence genetic variation in populations?
Organisms with advantageous traits are more likely to survive and pass on their genes, leading to genetic variation over generations.
List some example of inherited traits.
- Skin color
- Height
- Coat or feather color
- Ability to resist disease or pests
- Differences in protein function
- What is a locus on a chromosome?
- Why is it important in genetics?
- It is a specific location on a chromosome where a particular gene is located.
- It is important because it helps scientists identify and map genes, contributing to our understanding of inheritance and genetic traits.
Explain the concept of diploid and homologous chromosomes.
- Humans have two copies of each chromosome, one inherited from each parent, making them diploid.
- The two corresponding copies of a chromosome, one from each parent, are called homologous chromosomes.
Homologous chromosomes carry similar genetic information but may have different alleles for certain genes.
What does DNA stand for?
Deoxyribonucleic acid
How many genes does an individual typically have, and what do they determine?
An individual typically has 20,000 to 25,000 genes, each responsible for a different characteristic, such as eye color or hair color.
What is the significance of gametes in reproduction?
- They are special sex cells produced by reproductive glands (testes and ovaries), contain one copy of each gene.
- They combine during reproduction to create offspring with a random mixture of genes.
How does the expression of dominant and recessive genes work?
- Dominant genes are expressed even with one copy.
- Recessive genes require two copies for expression.
Dominant alleles are represented by uppercase letters, they mask the effect of recessive alleles, represented by lowercase letters.
For example, P (purple) is dominant over p (white).
What does the example (in the diagram) of two brown-eyed parents having a blue-eyed child demonstrate?
How recessive traits can be expressed in offspring even when both parents have dominant traits, due to the combination of genes during reproduction.
What incorrect belief about heredity did people have before Mendel’s discoveries?
People believed that traits were blended together, such as a child having a medium nose if one parent had a large nose and the other a small nose.
Define Mendel’s first Law.
(called the Law of Segregation)
It states that each allele for a trait will segregate, or separate, from its partner (during meiosis) so each gamete will only have one copy of the genetic material.
What is the significance of meiosis in Mendel’s Law of Segregation?
Meiosis is the process that halves the genetic information in gametes, ensuring that offspring have the correct amount of genetic material when gametes combine.
What are the possible genetic combinations for offspring from two Bb (purple flowered) pea plants (as shown in the diagram)?
- 25% chance of BB (purple)
- 50% chance of Bb (purple)
- 25% chance of bb (white)
What did Mendel’s experiments reveal about heredity?
It showed that traits are inherited in discrete units (genes) and can reappear in subsequent generations even if they are not visible in the parents.
When drawing punnet squares, how do we denote dominant and recessive alleles?
Dominant alleles are represented by uppercase letters, they mask the effect of recessive alleles, represented by lowercase letters.
For example, P (purple) is dominant over p (white).
Which process results in the formation of 4 haploid, genetically different gametes?
Meiosis
Describe Mendel’s Second Law?
Also known as The law of independent Assortment, it states that the outcome of one gene is not related to the outcome of another gene.
Explain how flipping a coin related to Mendel’s Second Law?
Just as the result of flipping a quarter does not affect the result of flipping a penny, the outcome of one gene does not affect the outcome of another gene according to Mendel’s Second Law.
What are linked genes?
Linked genes are genes that tend to be inherited together because they are located close to each other on the same chromosome.
Example: Red hair and freckles.
How did Mendel discover the law of independent assortment?
Through experiments on pea plants, observing the independent assortment of alleles for pea color (yellow or green) and pea shape (round or wrinkled).
What did Mendel observe when crossing pea plants for two traits?
That the ratios of 9 yellow round, 3 yellow wrinkled, 3 green round, and 1 green wrinkled, matching the predicted results from a Punnett square.
How can Mendel’s Second Law help in medical research?
Understanding independent assortment and gene linkage can help scientists discover the genetic basis of diseases and develop treatments by identifying linked genes.
Are all genes independently assorted according to Mendel’s second law?
No.
Some genes are linked together and do not assort independently, such as red hair and freckles.
What does it indicate if actual genetic results do not match the expected Punnett square results?
It indicates that the genes might be linked, meaning they do not assort independently and tend to be inherited together.
