Mendelian Genetics, Developmental Biology, and Molecular Genetics Overview

These flashcards review key points from Mendelian genetics, embryonic development, molecular genetics, and gene regulation to aid exam preparation.

Who is considered the father of modern genetics for his work with pea plants?

Gregor Mendel, an Austrian monk.

What three traits made Pisum sativum an ideal organism for Mendel’s experiments?

Multiple observable traits, self-fertilization with limited accidental cross-pollination, and fully fertile self-fertilized offspring.

In Mendel’s terminology, what is the P1 generation?

The true-breeding parental generation in a genetic cross.

What phenotype ratio did Mendel observe in the F2 generation of a monohybrid cross?

Approximately 3 dominant : 1 recessive.

State Mendel’s Principle of Segregation.

The two alleles for each trait separate during gamete formation, so each gamete carries only one allele.

State Mendel’s Principle of Independent Assortment.

Alleles of genes on different chromosomes assort independently during gamete formation.

What is complete dominance?

A situation where the heterozygote’s phenotype is identical to that of the homozygous dominant individual.

Define genotype.

The genetic makeup (allelic composition) of an organism.

Define phenotype.

The observable traits or characteristics of an organism.

What is a Punnett square used for?

To predict the probable genotypes and phenotypes of offspring from a genetic cross.

Which scientist coined the term ‘mutation’ for sudden heritable changes?

Hugo de Vries.

List the three major functions of fertilization.

Gene transmission from both parents, restoration of diploid chromosome number, and initiation of development.

What is cleavage in embryology?

Rapid mitotic divisions that convert the zygote into a multicellular embryo.

Name the three primary germ layers formed during gastrulation.

Ectoderm, mesoderm, and endoderm.

Which germ layer gives rise to the nervous system?

Ectoderm.

During which trimester are most major organ systems formed in humans?

The first trimester.

What hormone detected by pregnancy tests is secreted by the chorion?

Human chorionic gonadotropin (hCG).

What sugar is found in RNA but not in DNA?

Ribose.

Which nitrogenous base replaces thymine in RNA?

Uracil.

Name the three main types of RNA.

Messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

What is the function of mRNA?

Carries the genetic message from DNA to ribosomes for protein synthesis.

Describe the ‘cloverleaf’ structure region that attaches amino acids on tRNA.

The CCA 3′ end, where the activated amino acid is covalently attached.

Define genetic code.

The correspondence between mRNA nucleotide triplets (codons) and amino acids in proteins.

How many possible codons exist in the triplet genetic code?

64.

What is meant by degeneracy of the genetic code?

Most amino acids are specified by more than one codon.

Which codon serves as the universal start codon in translation?

AUG (codes for methionine).

List the three stop codons.

UAA, UAG, and UGA.

What enzyme synthesizes RNA during transcription?

RNA polymerase.

What are the three stages of transcription?

Initiation, elongation, and termination.

Which protein factors recognize stop codons during translation?

Release factors (RF1, RF2).

Define an operon.

A coordinated unit of gene expression consisting of structural genes, an operator, and a promoter.

In the lac operon, what molecule acts as the inducer?

Lactose (specifically allolactose).

What happens when the lac repressor binds the operator?

Transcription of lac structural genes is blocked.

Differentiate between positive and negative gene regulation.

Negative regulation uses a repressor to block transcription; positive regulation uses an activator to enhance transcription.

What is a cistron?

A DNA segment that codes for a single polypeptide chain.

Define muton.

The smallest unit of genetic material that can mutate to produce a phenotypic change—essentially one nucleotide pair.

What is a split gene?

A eukaryotic gene containing coding sequences (exons) interrupted by non-coding sequences (introns).

Explain wobble pairing.

Flexibility in base-pairing at the 3′ base of an mRNA codon, allowing one tRNA to recognize multiple codons.

What are polysomes?

Clusters of ribosomes simultaneously translating a single mRNA strand.

Which ribosomal subunit in bacteria contains the 16S rRNA?

The 30S small subunit.

What is the main control point for gene expression in most cells?

Regulation of transcription initiation.