Science Test Revision: Genetics and Evolution

Genetics and Evolution Flashcards

Why does DNA coil into a chromosome?

For preparation for DNA replication and cell division.

How many chromosomes do humans have?

Humans have 23 pairs of chromosomes (46 in total).

What are pairs of chromosomes called?

Homologous chromosomes.

How many pairs of autosomes do humans have?

22 pairs of autosomes (non-sex chromosomes).

How many pairs of sex chromosomes do humans have?

1 pair of sex chromosomes (XX or XY).

How many chromosomes are from each parent?

23 chromosomes from each parent.

How many chromosomes do somatic cells have?

Somatic cells (body cells) have 46 chromosomes (23 pairs).

How many chromosomes do sex cells have?

Sex cells (sperm or egg) have 23 chromosomes.

What does paternal copy mean?

Father

What does maternal copy mean?

Mother

What is a karyotype?

An individual’s complete set of chromosomes based on size, shape, and banding.

Define gene:

The fundamental unit of heredity, composed of DNA and carries the instructions for building and maintaining an organism’s structure and function.

Define allele:

A variant form of a gene that resides at the same location on a chromosome.

Define trait:

A specific, distinguishable characteristic of feature of an organism, passed down through genes and influenced by environmental factors.

Define inherited:

The passing traits from parent to child through genetic information.

Define chromosomes:

Thread – like structures found within the nucleus of a cell that carry genetic information in the form of genes.

What is mitosis?

A process of asexual reproduction in which the cell divides into 2 daughter cells, with an equal number of chromosomes in each resulting diploid cell.

What is the function of mitosis?

Cellular reproduction and general growth and repair of the body, cell replacement, and development.

What is meiosis?

A type of cellular reproduction in which the numbers if chromosomes are reduced by half through the separation of homologous chromosomes, producing 2 haploid cells.

What is the function of meiosis?

Genetic diversity through sexual reproduction.

Define dominant traits:

Needs only one present allele for that trait to be visible on the offspring. Represented by capital letters.

Define recessive traits:

Needs both alleles to be present to be visible on the offspring. Represented by lowercase letters.

Define genotype:

The genetic information of an organism. (The genes).

Define phenotype:

The observable physical traits of an organism. (What the genes make).

What do punnet squares show?

They show the likelihood of the offspring showing a trait (phenotype) from each parent.

Define heterozygous:

An individual has two different versions of the same gene/allele.

Define homozygous:

An individual inherited the same gene/allele of a specific trait, one from each parent.

Define homozygous dominate:

An individual that carries 2 dominate alleles for a specific trait.

Define homozygous recessive:

An individual that carries 2 recessive alleles for a specific trait.

What is complete dominance?

When one dominate allele is presented the recessive allele is taken over and masked.

What is incomplete dominance?

When both alleles are expressed (blend of both). 1 heterozygous and 2 homozygous traits.

What is codominance?

Both phenotypes are expressed in the offspring. This is like incomplete dominance but both parental traits are heterozygous.

What are multiple alleles?

Some genes have more than 2 alleles.

Define adaption:

Adaption happens when an organism needs to change, the way they look (structural), what they eat (physiological), or how they behave (behavioural) to better suit their environment which can give them a survival advantage.

Define natural selection:

Natural selection happens when there is a mutation in the genes during cell reproduction. Organisms with heritable traits that make them better suited for their environment are more likely to survive and reproduce, meaning they can pass down advantageous traits to their offsprings which will lead to the increase of the population.

Why is Lamarck's theory of evolution incorrect?

Because he proposes that an animal makes changes in its lifetime to suit their needs. This theory contradicts the principles of genetic and lacks factual support.

Why is Darwin's theory of evolution correct?

Because he imposes that an organism changes and adapts over time through a process of inherited variation and natural selection meaning that individuals that are best suited will survive and pass the advantageous trait on for later generations.

What are the 4 selection pressures during the stages of natural selection?

Predation, climate factors, diseases, and competition.

Define predation:

The interaction where one organism kills and consumes another organism.

Define climate factors:

The environmental conditions like temperature, rainfall, light, and gases.

Define variation:

Individuals in a population differ in some traits. Variation can be physical features, behaviours bodily functions, or resistance to disease.

Define inheritance:

The trait inherited (passed down from parent to offspring). The variation comes from random mutation and recombination during sexual reproduction.

What is convergent evolution?

Convergent evolution is when species that don’t share the same ancestors adapt to have similar characteristics due to similar selection pressures and similar variations selected for that species.

What is divergent evolution?

Divergent evolution is when species share the same ancestor but adapted very differently with different characteristics due to different selection pressures therefore having different variations selected for them.

What is a phylogenetic tree?

A phylogenetic tree is a diagram to show the evolutionary relationship between groups of organisms or species.

What does the root of the phylogenetic tree represent?

The root of the tree represents the most recent common ancestor of all the species in the tree.

What do the branches of the phylogenetic tree represent?

Each line represents a lineage, or a series of ancestors leading up to a species.

What are fossils?

Fossils are physical evidence for evolution because it shows the organisms that’s lived in the past can shows how the species have changed over time.

Define homologous structures:

Homologous structures are body parts in different animals that come from the same ancestor. They might look different and do different things now, but they started from the same basic structure long ago.

Define analogous structures:

Analogous structures are body parts that do similar jobs in different animals, but they don’t come from the same ancestor. They evolved separately to help animals do similar things in their environment.