Biology Notes Review: Inheritance, Genome, Reproduction, Evolution, and Classification

A comprehensive set of QA flashcards covering inheritance, genome, protein synthesis, reproduction, meiosis, sex determination, Mendel, evolution, natural selection, speciation, and modern classification systems.

What is a gamete?

An organism’s reproductive cell that contains half the normal number of chromosomes (23 in humans).

What is a chromosome?

A structure in the nucleus made up of a long DNA molecule that carries genetic information.

What is a gene?

A short section of DNA that codes for a protein and contributes to a characteristic

What is an allele?

A different form of a gene; humans have two alleles for each gene, inherited from each parent.

What is a dominant allele?

Only one copy is needed for the allele to be expressed and the dominant phenotype to appear.

What is a recessive allele?

Two copies are needed for the allele to be expressed and the recessive phenotype to appear.

What does homozygous mean?

Both inherited alleles are the same (two dominant or two recessive alleles).

What does heterozygous mean?

One inherited allele is dominant and the other is recessive.

What is genotype?

The combination of alleles an individual has (e.g., Aa).

What is phenotype?

The physical characteristics observed in an individual (e.g., eye colour).

What is the genome?

The complete genetic information of an organism; the genotype interacts with the environment to produce the phenotype, showing continuous or discontinuous variation.

What is genetic variance?

All variants (alleles) arise from mutations; most have no effect because much DNA is non-coding, but some can influence phenotype, and a few can change it if in coding regions.

What happens if a mutation occurs in a coding region of DNA?

It can alter the activity of the protein by changing its structure, such as the active site, potentially affecting function.

What happens if a mutation occurs in a non-coding region of DNA?

It can affect gene expression, for example by stopping transcription of mRNA.

Describe the main steps of protein synthesis.

In nucleus, DNA is transcribed to mRNA; mRNA exits to the cytoplasm and ribosomes; bases on mRNA are read in threes (codons) to code for amino acids; amino acids are brought by tRNA and linked to form a protein, which folds into a 3D structure.

What is an advantage of sexual reproduction?

Produces genetic variation in offspring, which can help populations survive changing environments.

What is an advantage of asexual reproduction?

Requires only one parent, no need to find a mate, and tends to produce many identical offspring; uses less energy.

What is meiosis?

The formation of four non-identical haploid cells (gametes) from a single diploid cell, with chromosome number halved and genetic variation introduced by shuffling.

What is the difference between diploid and haploid cells?

Diploid cells have two complete sets of chromosomes; haploid cells have one set (as in gametes).

Why are gametes haploid?

Meiosis halves the chromosome number to produce gametes with one copy of each chromosome.

What is a Punnett square used for?

To predict the probabilities of offspring genotypes and phenotypes from parental alleles.

What do uppercase and lowercase letters represent in Mendelian crosses?

Uppercase letters represent dominant alleles; lowercase letters represent recessive alleles.

What is sex determination in humans?

Humans have 23 pairs of chromosomes; the 23rd pair (sex chromosomes) determines sex: XX for female, XY for male; meiosis in parents leads to a 50% chance of a boy or a girl.

Which parent always passes on an X chromosome in humans?

Females pass on an X chromosome in their eggs

What did Mendel conclude about inheritance?

Offspring inherit hereditary units from each parent; units can be dominant or recessive and cannot be blended; they are inherited as discrete factors.

How are genes related to chromosomes?

Genes are located on chromosomes and are the units that are passed on during inheritance.

What is evolution?

A change in the inherited characteristics of a population over time through natural selection, which can lead to the formation of new species.

What is natural selection?

Variation exists in a population; individuals with advantageous traits are more likely to survive and reproduce, increasing those alleles in the population over generations.

What is speciation?

When populations become isolated and accumulate different genetic changes, eventually leading to the ability to interbreed and form a new species.

What is artificial classification?

Classification based on observable features and human judgment (Linnaeus' system: kingdom, phylum, class, order, family, genus, species).

What is natural classification?

Classification using molecular evidence (biochemistry, DNA) and phylogenetics to determine relationships between organisms.

what are the three domains?

Archaea, Bacteria, and Eukaryota.

What is binomial nomenclature?

A worldwide naming system using two parts: genus and species (e.g., Harmonia axyridis for the ladybird).

What kinds of evidence support evolution?

Fossils showing anatomical changes over time and antibiotic resistance in bacteria.

What does antibiotic resistance illustrate about evolution?

Exposure to antibiotics creates a selection pressure; resistant alleles increase in frequency, leading to resistant populations

How has the human genome contributed to biology?

Studying the genome helps identify genes linked to diseases, understand inherited disorders, and trace human migration patterns.

What is the binomial example given for a ladybug?

Harmonia axyridis (genus Harmonia, species axyridis).