Exam Revision

what chemical carries the genetic instructions for cell development?

Deoxyribonucleic acid (DNA)

How did Watson and Crick describe the structure of DNA?

They described it as a double helix, consisting of two strands twisted around each other.

how many chromosomes is present in a fertilized human egg?

A fertilized human egg contains 46 chromosomes, which are arranged in 23 pairs.

what is the term for alternate versions of a gene?

Alleles

What does the appearance of pink snapdragons when red and white are crossed demonstrate?

Incomplete dominance in genetics.

If a pure black and a pure white domestic fowl produce a speckled hybrid, what is the chance of speckled offspring when this hybrid is crossed with a pure black fowl?

The chance of speckled offspring is 50%.

If a woman has had four sons, what is the probability of her next child being a girl?

The probability remains 50%, as the gender of each child is independent of previous children.

What disorder is associated with an abnormality in chromosome 21?

Down syndrome, a genetic disorder caused by an extra chromosome 21.

What best describes a clone?

A genetically identical copy of an organism.

Which two components are consistent in every nucleotide of DNA?

A phosphate group and a sugar.

Where are genes located in the human body?

Genes are located on chromosomes within the cell nucleus.

A brown animal crossed with a white one produces only brown offspring. What does this indicate about the brown gene?

It is dominant over the white gene.

Does having a boy first affect the likelihood of having a girl next?

No, the likelihood of having a boy or girl remains roughly equal regardless of previous births, as it is determined by the X and Y chromosomes.

What is an autosome?

An autosome is a chromosome that is not a sex chromosome and is involved in determining the non-sexual traits of an organism.

What term is used for the two chromosomes that make up the 23rd pair?

Sex chromosomes

If both parents are carriers of cystic fibrosis but do not have the disease, what are the chances their child will have it?

If both parents are carriers of cystic fibrosis, there is a 25% chance their child will be affected by the disease.

What was the primary goal of the Human Genome Project?

The primary goal of the Human Genome Project was to map and understand all the genes of the human species, including their sequences and functions.

Which base always pairs with adenine in DNA?

Thymine

Which base always pairs with guanine in DNA?

Cytosine

To which class do humans belong?

Humans belong to the class Mammalia within the animal kingdom. This class is characterized by warm-blooded vertebrates that possess mammary glands and typically have hair or fur.

Which process can lead to variation within a species?

This process is called evolution, which involves changes in genetic traits over generations through mechanisms such as natural selection, mutation, and genetic drift.

Who is generally credited with proposing the theory of evolution?

Charles Darwin is generally credited with proposing the theory of evolution through natural selection.

What part of mammals, reptiles, amphibians, and birds share a similar structure?

Limbs adapted for movement and support.

What does a gene pool represent?

A gene pool represents the total collection of genes and their alleles within a population, reflecting genetic diversity and potential for variation in traits.

What percentage of all species that have ever lived are estimated to be extinct?

Approximately 99 percent.

Why is genetic variety within a species essential for survival?

Genetic variety within a species is essential for survival as it enhances adaptability to changing environments, increases resilience against diseases, and plays a crucial role in the overall health and viability of populations.

Why is natural selection described as 'survival of the fittest'?

Natural selection is described as 'survival of the fittest' because it refers to the process by which individuals with advantageous traits are more likely to survive, reproduce, and pass those traits to the next generation, thereby shaping the genetic makeup of a population over time.

What is meant by the term "common ancestor"?

An ancestral group of organisms that is shared by multiple lineages.

What is convergent evolution?

Convergent evolution is the process where organisms not closely related independently evolve similar traits as a result of having to adapt to similar environments or ecological niches

What caused the decrease in the tan mouse population?

Selective pressures leading to differences in survival/reproduction

What environmental change could lead to an increase in the tan mouse population?

an increase in light-colored or sandy terrain

What is the most serious consequence for a species with a shrinking gene pool?

reductions in genetic diversity, reproductive fitness, and a limited ability to adapt to environmental change increasing the risk of extinction.

What best defines artificial selection?

the process where humans intentionally breed organisms with desirable traits to produce offspring with those same traits

What is a notable example of adaptive evolution?

the evolution of the peppered moth in eighteenth- and nineteenth-century England

What was the name of the supercontinent that included all landmasses?

Pangaea