Molecular Genetics Study Guide

This collection of flashcards covers key concepts in molecular genetics, including DNA structure and replication, protein synthesis, and meiosis.

What is the structure of a nucleotide composed of?

A nucleotide is composed of a sugar, a phosphate group, and a nitrogenous base.

Which three scientists contributed to the discovery of the double helix structure of DNA?

James Watson, Francis Crick, and Rosalind Franklin.

What are the base pairing rules of DNA?

Adenine pairs with Thymine, and Cytosine pairs with Guanine.

What distinguishes purines from pyrimidines in DNA?

Purines are adenine and guanine (two rings), while pyrimidines are cytosine and thymine (one ring).

How should the ends of a DNA molecule be labeled?

The ends should be labeled as 5' and 3'.

What is the process of DNA replication summarized?

DNA replication involves unwinding the double helix, complementary base pairing, and synthesis of new strands by enzymes like DNA polymerase.

What is the difference between the leading strand and the lagging strand during DNA replication?

The leading strand is synthesized continuously, while the lagging strand is synthesized in short segments called Okazaki fragments.

Why is DNA replication described as semi-conservative?

Because each new DNA molecule contains one original strand and one new strand.

How can you identify a nucleic acid as DNA or RNA?

DNA contains deoxyribose and thymine, while RNA contains ribose and uracil.

What is the Central Dogma of Genetics?

The Central Dogma describes the flow of genetic information from DNA to RNA to protein.

Why is a two-step process necessary to make proteins?

Because DNA is transcribed into RNA, which is then translated into protein.

What are the three essential types of RNA involved in protein synthesis?

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

Describe the location and steps of transcription.

Transcription occurs in the nucleus, where DNA is transcribed into pre-mRNA by RNA polymerase.

How is pre-mRNA modified after transcription?

Pre-mRNA undergoes splicing to remove introns and add a 5' cap and poly-A tail.

Summarize the steps of translation.

Translation occurs in the cytoplasm, where mRNA is read by ribosomes, and tRNA brings amino acids to form a polypeptide.

What is a polypeptide?

A polypeptide is a chain of amino acids linked by peptide bonds, which can fold into a functional protein.

Why is regulation of gene expression important?

Regulating gene expression ensures that proteins are produced only when needed, maintaining cellular function.

What is the difference between epigenetics and mutations?

Epigenetics involves reversible changes in gene expression without altering DNA sequence, while mutations involve permanent changes to the DNA sequence.

What is the difference between somatic cells and gametes?

Somatic cells are diploid body cells, while gametes are haploid reproductive cells.

Differentiate between autosomes and sex chromosomes.

Autosomes are non-sex chromosomes, while sex chromosomes determine an individual's sex (X and Y in humans).

Why do cells undergoing meiosis divide twice?

Meiosis consists of two divisions to reduce chromosome number from diploid to haploid.

What is the purpose of meiosis I and meiosis II?

Meiosis I separates homologous chromosomes, while meiosis II separates sister chromatids.

What is the significance of crossing over in meiosis?

Crossing over allows for genetic recombination, increasing genetic diversity.

What are the key differences between meiosis and mitosis?

Meiosis produces four genetically diverse haploid cells, while mitosis produces two identical diploid cells.

How can you identify a cell as haploid or diploid?

Cells are haploid if they contain one set of chromosomes (n) and diploid if they contain two sets (2n).

Define a gene.

A gene is a segment of DNA that codes for a specific protein.

What is a chromosome?

A chromosome is a tightly coiled structure of DNA and proteins containing genetic information.

What does pre-mRNA refer to?

Pre-mRNA is the initial transcript of DNA that is processed to form mature mRNA.

What are introns?

Introns are non-coding regions of RNA that are removed during RNA processing.

What is Chargaff's Rule?

Chargaff's Rule states that in DNA, the amount of adenine equals thymine and the amount of cytosine equals guanine.

What are exons?

Exons are coding regions of RNA that remain after splicing and are translated into proteins.

What is an RNA primer?

An RNA primer is a short strand of RNA that provides a starting point for DNA synthesis.

What does antiparallel mean in DNA structure?

Antiparallel refers to the opposite orientation of the two strands of DNA (one runs 5' to 3' and the other 3' to 5').

What is a diploid cell?

A diploid cell contains two complete sets of chromosomes, one from each parent.

What is a haploid cell?

A haploid cell contains a single set of unpaired chromosomes.

What is a karyotype?

A karyotype is a visual representation of an individual's chromosomes, used to assess genetic conditions.

What is a codon?

A codon is a sequence of three nucleotide bases in mRNA that codes for a specific amino acid.

What is an anticodon?

An anticodon is a sequence of three nucleotide bases in tRNA that pairs with a codon in mRNA.

What is an amino acid?

An amino acid is a building block of proteins, linked together by peptide bonds.

What is sexual reproduction?

Sexual reproduction is the process by which organisms combine genetic material from two parents to produce offspring.

What is fertilization?

Fertilization is the fusion of male and female gametes to form a zygote.

What are homologous chromosomes?

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

What are sister chromatids?

Sister chromatids are identical copies of a chromosome formed during DNA replication.

What is a tetrad in meiosis?

A tetrad is a group of four chromatids formed during the prophase of meiosis I, consisting of two homologous chromosomes.