UNIT1 - BIOLOGICAL ASPECTS - GENETICS Flashcards
What are genes and what do they do?
Genes are units of heredity that maintain their structural identity from one generation to another. They are located on chromosomes and carry information that determines traits.
What are chromosomes and how many do humans have?
Chromosomes are microscopic strands of nucleic acid and proteins that carry genes. Humans normally have 46 chromosomes (23 pairs).
What is DNA and what is its structure?
DNA (deoxyribonucleic acid) is the principal carrier of genetic information. It has a double helix structure, like a twisted ladder, with base pairs (adenine-thymine, guanine-cytosine).
What is the genetic code?
The genetic code is the “instruction manual” in DNA that tells the cell how to make specific proteins.
What is the difference between homozygous and heterozygous?
Homozygous means having the same genes on two copies of a chromosome. Heterozygous means having an unmatched pair of genes.
What is RNA and what are its main types?
RNA (ribonucleic acid) is a single-strand chemical that directs protein synthesis. The main types are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
What is the difference between dominant and recessive genes?
A dominant gene shows its effect in either the homozygous or heterozygous condition. A recessive gene shows its effect only in the homozygous condition.
What are sex-linked genes?
Genes located on the sex chromosomes (usually the X chromosome).
What are sex-limited genes?
Genes present in both sexes but active only in one sex (e.g., beard growth in men).
What is a mutation?
A permanent change in the genetic material of an organism.
What are the two main types of mutations?
Chromosomal mutations (changes in chromosome number or arrangement) and point mutations (changes in DNA base sequence).
What is the difference between somatic and germ-line mutations?
Somatic mutations occur in body cells and are not inherited. Germ-line mutations occur in reproductive cells and can be inherited.
What are microduplications and microdeletions?
Microduplications are when a small part of a chromosome appears twice. Microdeletions are when a small part of a chromosome is missing.
What is epigenetics?
Heritable changes in gene function that are not due to changes in the DNA base sequence. It involves genes being switched on or off based on experience.
How can experiences affect gene expression?
Experiences can lead to epigenetic changes, affecting whether certain genes are activated or not. These changes can sometimes be passed down a generation or two.
What is heritability?
The extent to which variations in a characteristic are due to genetic differences.
What are the three main methods used to study heritability?
Twin studies, adoption studies, and the candidate gene approach
What are the limitations of twin and adoption studies?
Twin studies: Difficult to separate genetic and environmental influences completely. Adoption Studies: Biological mother’s prenatal environment also influences the child.
What is the candidate gene approach?
An attempt to identify specific genes linked to certain behaviors.
What is the general conclusion about nature vs. nurture?
Most research suggests that behavior is not determined by genes alone, but by the interaction of genes and specific environmental conditions.
What are monozygotic twins?
Identical twins that develop from a single fertilized egg and share the same genetic makeup
What are dizygotic twins?
Fraternal twins that develop from two separate fertilized eggs and share about 50% of their genes, like ordinary siblings.
Why are twin studies useful for studying heritability?
By comparing monozygotic and dizygotic twins, researchers can get an idea of how much variation in a trait is due to genes versus environment.
What is the logic behind adoption studies?
Comparing adopted children to their biological and adoptive parents can help tease apart genetic and environmental influences.
What are some of the challenges with the candidate gene approach?
It can be difficult to isolate the effects of a single gene, and many behaviors are likely influenced by multiple genes and environmental factors.
What is Phenylketonuria (PKU)?
A genetic disorder where a person cannot metabolize the amino acid phenylalanine, leading to impaired brain development.
How can PKU be managed?
Through a low-phenylalanine diet, which is an example of how environmental manipulation can influence a genetic condition.
What is the ultimate question about the genetic basis of human behavior?
To what extent are our behaviors and traits shaped by our genes (nature) versus our environment and experiences (nurture)?
