Biology chapter 4 Genetic Information, Variation, and Relationships between Organisms

DNA, Genes, and Chromosomes Protein Synthesis Genetic Diversity and Adaptation Species and Taxonomy Biodiversity within a Community Investigating Diversity Variation in Populations

What is a gene?

A gene is a segment of DNA that contains the coded instructions for making a specific protein or RNA molecule.

How many chromosomes do humans have?

Humans have 46 chromosomes, arranged in 23 pairs.

What is the role of histones in chromosomes?

Histones help package and organize DNA into a compact, dense structure, allowing it to fit inside the cell nucleus.

What is the difference between a haploid and diploid cell?

A haploid cell has one complete set of chromosomes (n), while a diploid cell has two sets (2n), one from each parent.

What are homologous chromosomes?

Homologous chromosomes are pairs of chromosomes that have the same genes at the same loci but may have different alleles.

What is the function of the centromere?

The centromere is the region of a chromosome where sister chromatids are joined and where spindle fibers attach during cell division.

What is a mutation?

A mutation is a change in the nucleotide sequence of DNA, which can affect the structure and function of genes.

What are exons and introns?

Exons are coding regions of a gene that are expressed as proteins, while introns are non-coding regions that are removed during RNA splicing.

What is a promoter region in DNA?

A promoter is a DNA sequence that signals the start of a gene, where RNA polymerase binds to initiate transcription.

What is chromatin?

Chromatin is the complex of DNA and proteins (histones) that forms chromosomes within the nucleus of eukaryotic cells.

What is a codon?

A codon is a sequence of three nucleotides in mRNA that specifies an amino acid or a start/stop signal for protein synthesis.

What is a gene locus?

A locus is the specific physical location of a gene or other significant sequence on a chromosome.

What is a genome?

A genome is the complete set of genetic material in an organism, including all of its genes and non-coding sequences.

Where does transcription occur?

In the nucleus of eukaryotic cells.

What is the role of RNA polymerase during transcription?

RNA polymerase synthesizes mRNA by reading the DNA template strand.

What is the difference between the template strand and the coding strand in DNA?

The template strand is the DNA strand that RNA polymerase reads to synthesize mRNA, while the coding strand has the same sequence as the mRNA (except with thymine instead of uracil).

What is the function of mRNA?

mRNA carries genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm.

Where does translation occur?

In the ribosomes located in the cytoplasm.

What is the role of tRNA during translation?

tRNA brings the correct amino acid to the ribosome according to the codon on the mRNA.

What is an anticodon?

An anticodon is a sequence of three nucleotides on a tRNA molecule that is complementary to an mRNA codon.

What is the role of ribosomal RNA (rRNA)?

rRNA, along with proteins, makes up the ribosomes which facilitate the binding of tRNA to mRNA and the formation of peptide bonds between amino acids.

What is the start codon for translation, and which amino acid does it code for?

The start codon is AUG, and it codes for the amino acid methionine.

What enzyme is responsible for transcription?

RNA Polymerase

Describe the initiation of translation.

The small ribosomal subunit binds to the mRNA at the start codon, followed by the binding of the initiator tRNA (carrying methionine), and then the large ribosomal subunit assembles to form the complete ribosome.

Describe the elongation process in translation.

During elongation, tRNAs bring amino acids to the ribosome, matching their anticodons with mRNA codons. Peptide bonds form between amino acids, and the ribosome moves along the mRNA.

What happens during the termination of translation?

When a stop codon is reached, the release factor binds to the ribosome, causing the newly synthesized polypeptide to be released and the ribosome to disassemble.

What happens during the initiation stage of transcription?

RNA polymerase binds to the promoter region and unwinds the DNA to begin RNA synthesis.

What occurs during the elongation stage of transcription?

RNA polymerase moves along the DNA template strand, adding RNA nucleotides in a 5' to 3' direction to elongate the mRNA strand.

What happens during the termination stage of transcription?

RNA polymerase reaches a terminator sequence, signaling the end of transcription, and the newly synthesized mRNA is released.

What is RNA splicing?

The process of removing introns from pre-mRNA and connecting the exons to form the final mRNA.

What is the shape of tRNA?

tRNA has a cloverleaf structure in two dimensions and an L-shaped structure in three dimensions.

What is genetic diversity?

Genetic diversity refers to the variety of genetic information within a population or species.

Why is genetic diversity important?

Genetic diversity allows populations to adapt to changing environments, reduces the risk of extinction, and provides the raw material for evolution.

What factors contribute to genetic diversity?

Mutations, gene flow (migration), genetic recombination (crossing over and independent assortment during meiosis), and natural selection.

How do mutations contribute to genetic diversity?

Mutations introduce new alleles into a population's gene pool, increasing genetic variation.

What is gene flow?

Gene flow is the movement of alleles between populations through migration of individuals.

How does genetic recombination contribute to genetic diversity?

Genetic recombination during meiosis results in new combinations of alleles on chromosomes, increasing genetic variation.

What is natural selection?

Natural selection is the process by which individuals with advantageous traits for survival and reproduction are more likely to pass on their genes to the next generation.

How does natural selection lead to adaptation?

Natural selection acts on the variation within a population, favoring traits that enhance survival and reproductive success in a particular environment, leading to adaptation over time.

What are adaptations?

Adaptations are traits or characteristics that increase an organism's fitness and survival in its environment

What are the consequences of low genetic diversity?

Low genetic diversity can reduce a population's ability to adapt to environmental changes, increase susceptibility to diseases, and elevate the risk of extinction.

What is genetic drift?

Genetic drift is the random change in allele frequencies in a population due to chance events, particularly in small populations.

How does genetic drift affect genetic diversity?

Genetic drift can reduce genetic diversity by causing the loss of alleles from a population's gene pool.

How does sexual reproduction contribute to genetic diversity?

Sexual reproduction introduces new combinations of alleles through meiosis, fertilization, and genetic recombination, increasing genetic variation within a population.

How can mutations arise?

Mutogenic agents, change in DNA replication

What is a mutogenic agent?

increase the rate of gene mutations by damaging DNA / DNA pool e.g. tobacco, virus, radiation

What is point mutation?

Change in single base

5 types of mutation

Substitution, deletion, inversion, addition, duplication

give the 3 effects of protein mutations have

mis sense, silence, non sense

What is a silent effect

Change in base, but same amino acid is formed

What is a mis sense effect?

Change amino acids, so protein function changes

What is non sense effect?

Early stop of triplet, so protein is shorter, so doesn’t function at all

Genetic diversity is measured by…

Observations, gene technology

Three types of adaptations

1. Anatomical

2. Physiological

3. Psychological

What is taxonomy?

Taxonomy is the science of classifying organisms based on characteristics and relationships. It involves naming, describing, and organizing species into a systematic framework.

Who is considered the father of modern taxonomy?

Carl Linnaeus is considered the father of modern taxonomy. He developed the binomial nomenclature system for naming species.

What is binomial nomenclature?

Binomial nomenclature is a two-part naming system for organisms, consisting of the genus name (capitalized) and the species name (lowercase), both italicized or underlined, e.g., Homo sapiens.

What are the major taxonomic ranks in order from broadest to most specific?

The major taxonomic ranks are: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

What is a species?

A species is the most specific level of organism classification, defined as a group of individuals that can interbreed and produce fertile offspring.

What is a phylogenetic tree?

A phylogenetic tree is a diagram that represents the evolutionary relationships among various biological species based on similarities and differences in genetic or physical traits.

What is the role of taxonomy in biodiversity conservation?

axonomy helps identify and classify species, assess their conservation status, and prioritize efforts to protect biodiversity by understanding the relationships and significance of different species within ecosystems.

What is the phylogenetic species concept?

The phylogenetic species concept defines a species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life.

What is biodiversity?

Biodiversity refers to the variety and variability of life forms within a given ecosystem, biome, or the entire Earth, including species diversity, genetic diversity, and ecosystem diversity.

What is species diversity?

Species diversity is the number of different species and the relative abundance of each species within a community.

What is genetic diversity?

Genetic diversity refers to the variation of genes within a species, which is crucial for populations to adapt to changing environments.

How is species richness defined?

Species richness is the number of different species present in a particular area or community.

What is an ecological niche?

An ecological niche is the role and position a species has in its environment, including all its interactions with biotic and abiotic factors.

What is the difference between primary and secondary succession?

Primary succession occurs in lifeless areas where soil has yet to form, while secondary succession occurs in areas where a disturbance has destroyed a community but left the soil intact.

How can you compare species and how closely related they are?

DNA base sequence of common  genes (or mRNA transcribed from them).

Amino acid sequence of common  proteins.

 Immunology of common proteins.

 Courtship behaviours. 

Anatomical similarities

Why do we classify organisms?

• Makes them easier to study.

• Allows us to make sense of the living world.

• Helps us understand how living things are related. 

• Helps us recognise biodiversity.

Gives scientists a common language

What is courtship behaviour?

Courtship behaviour is a set of display behaviours by which animals attract mates and exhibit their readiness to mate.

Why is courtship behaviour important?

Courtship behaviour is important for species recognition, attracting mates, and ensuring reproductive success.

How does courtship behaviour contribute to species recognition?

Courtship behaviours often include species-specific signals and displays that help individuals recognize members of their own species, preventing hybridization.