exam 4

Phenotype

The observable physical or biochemical characteristics of an organism, determined by both genetic makeup and environmental influences.

Genotype

The genetic constitution of an individual, often in terms of alleles.

Gene

A segment of DNA that contains the information to code for a functional product, typically a protein.

Allele

One of two or more versions of a gene that are found at the same place on a chromosome.

Homozygous

Having two identical alleles for a particular gene.

Heterozygous

Having two different alleles for a particular gene.

True-breeding

Organisms that, when mated, consistently produce offspring with a specific trait.

Dominant allele

An allele that expresses its phenotype even in the presence of a recessive allele.

Recessive allele

An allele that only expresses its phenotype when homozygous.

Punnett square

A diagram used to predict the genetic outcome of a cross between two individuals.

Dihybrid cross

A genetic cross that examines the inheritance of two different traits.

Monohybrid cross

A genetic cross that examines the inheritance of a single trait.

Incomplete dominance

A form of inheritance in which one allele does not completely dominate another, resulting in a third phenotype.

Polygenic inheritance

A mode of inheritance where a trait is controlled by multiple genes.

Double helix

The structure formed by double-stranded molecules of nucleic acids such as DNA.

Antiparallel strands

Refers to the two strands of DNA running in opposite directions.

Hydrogen bond

A type of weak chemical bond that is important in maintaining the structure of DNA.

Chargaff's Rule

The principle stating that in DNA, the amount of adenine equals thymine and the amount of cytosine equals guanine.

Semi-conservative replication

The process of DNA replication where each new DNA molecule contains one original strand and one new strand.

Helicase

An enzyme that unwinds and separates the double-stranded DNA into single strands.

DNA polymerase

An enzyme that synthesizes new DNA strands by adding nucleotides complementary to the template strand.

Leading strand

The strand of DNA that is synthesized continuously during replication in the 5' to 3' direction.

Lagging strand

The strand of DNA that is synthesized discontinuously in short segments during replication.

Okazaki fragments

Short sequences of DNA synthesized on the lagging strand during replication.

Ligase

An enzyme that joins together Okazaki fragments during DNA replication.

Nucleotide excision repair

A DNA repair mechanism that removes and replaces damaged sections of DNA.

Thymine dimer

A DNA lesion caused by the covalent bonding of two adjacent thymine bases, often due to UV exposure.

Central Dogma

The framework for understanding the transfer of genetic information from DNA to RNA to protein.

Transcription

The process of synthesizing RNA from a DNA template.

Translation

The process of synthesizing a protein from an mRNA template.

RNA polymerase

An enzyme that synthesizes RNA from a DNA template during transcription.

mRNA

Messenger RNA, which carries the genetic information from DNA to the ribosome for protein synthesis.

tRNA

Transfer RNA, which carries amino acids to the ribosome during protein synthesis.

Promoter

A DNA sequence that defines where transcription of a gene by RNA polymerase begins.

Exon

A sequence of DNA that codes for a protein and is expressed in RNA.

Intron

A non-coding sequence of DNA that is not expressed in RNA.

Splicing

The process of removing introns and joining exons in a pre-mRNA transcript.

Start codon (AUG)

The codon that signals the start of translation.

Universality (of genetic code)

The principle that the genetic code is the same in almost all organisms, allowing gene transfer between species.

Ribosome

The molecular machine that synthesizes proteins by translating mRNA.

A-site

The site on the ribosome where the incoming tRNA molecule binds during translation.

P-site

The site on the ribosome where the tRNA carrying the growing polypeptide chain is located.

E-site

The site on the ribosome where empty tRNA exits after amino acid transfer.

Anticodon

A sequence of three nucleotides on a tRNA that is complementary to a codon on mRNA.

Acceptor stem

The region of tRNA that binds to the amino acid.

Stop codon

A codon that signals the termination of translation.

Mutation

A change in the DNA sequence that can lead to changes in phenotype.

Substitution mutation

A mutation that replaces one nucleotide with another in the DNA sequence.

Insertion mutation

A mutation that adds one or more nucleotides into the DNA sequence.

Deletion mutation

A mutation that removes one or more nucleotides from the DNA sequence.

Inversion mutation

A mutation where a segment of DNA is reversed and reinserted into the sequence.

Denaturation (protein)

The process by which proteins lose their structure and function due to external stress.

Detergent (in DNA extraction)

A substance used to break down cell membranes, facilitating the release of DNA.

Genotypic ratio

The ratio of different genotypes that result from a genetic cross.

Phenotypic ratio

The ratio of different phenotypes that result from a genetic cross.

Why Mendel used peas, not cattle

Peas were easier to cultivate, had identifiable traits, and could be easily crossbred.

Law of Dominance

The principle stating that some alleles are dominant and others are recessive.

Law of Segregation

The law that states that allele pairs separate during gamete formation.

Law of Independent Assortment

The law stating that genes for different traits are inherited independently of each other.

Interpreting Punnett Squares

The skill of analyzing Punnett squares to predict genetic crosses.

Non-Mendelian inheritance

Patterns of inheritance that do not adhere to Mendel’s laws, such as incomplete dominance and polygenic inheritance.

DNA structure

Refers to the composition and organization of DNA, including base pairing and double helix formation.

DNA Replication process

The series of steps that occur to duplicate DNA molecules, including initiation and elongation.

Okazaki fragments & lagging vs. leading

Short DNA segments on the lagging strand compared to the continuous synthesis on the leading strand.

DNA repair basics

Fundamental mechanisms of repairing DNA, including nucleotide excision repair and its role in fixing UV-induced damage.

Central Dogma process

The flow of genetic information from DNA to RNA to protein.

Transcription steps

The detailed phases of transcription: initiation, elongation, and termination.

Translation steps

The phases involved in translation: initiation, elongation, and termination.

Post-transcriptional processing

The modifications that mRNA undergoes after transcription, including splicing.

Universality of the genetic code

The concept that the genetic code is consistent across most organisms, which has implications for gene transfer.

Determining amino acid sequence from mRNA

The process of translating nucleotide sequences into polypeptide chains.

tRNA function and structure

The role of transfer RNA in bringing amino acids to ribosomes and its structural components.

Mutation types

Various alterations of DNA that can lead to different biological effects.

DNA extraction

The process of isolating DNA from cells, utilizing substances like detergents for effective extraction.

Sex determination

The mechanism by which the sex of an organism is determined based on parental genetic contributions.

Protein stability/denaturation by temperature

The impact of temperature on the structure and function of proteins.