Human Genome Architecture Lecture

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Questions and Answers

What is the main function of mtDNA?

To regulate the synthesis of transfer RNA.

To control the overall structure of the cell.

To provide instructions for the production of ribosomal RNA.

To encode for proteins involved in cellular respiration. (correct)

What is the primary role of nuclear DNA?

To regulate the flow of molecules across the cell membrane.

To provide structural support for the nucleus.

To store genetic instructions for building and maintaining the cell. (correct)

To participate in the process of protein synthesis.

How is nuclear DNA packaged within the cell?

It is dispersed throughout the cytoplasm in a free form.

It is folded into a single, compact structure.

It is organized into multiple, linear chromosomes. (correct)

It exists as a circular loop within the nucleus.

What is the significance of the repetitive DNA sequences found in the genome?

They have no known function, but they represent a significant part of the genome. (D) Signup and view all the answers

What is the significance of the short (p) and long (q) arms of a chromatid?

They are responsible for the proper alignment of chromosomes during cell division. (D) Signup and view all the answers

Why is proper chromosome condensation important during mitotic entry?

It makes it possible to visualize and examine the karyotype. (C) Signup and view all the answers

Which of the following statements is TRUE about human mitochondrial DNA (mtDNA)?

mtDNA replication is independent of the nuclear DNA replication cycle and is therefore a less precise process. (A), mtDNA is a circular molecule, about 16,569 base pairs long. (B) Signup and view all the answers

What is the approximate percentage of the human genome that encodes proteins?

1.5% (B) Signup and view all the answers

What is the consequence of meiotic nondisjunction?

It results in the production of daughter cells with an abnormal number of chromosomes. (B) Signup and view all the answers

Which of the following best describes the relationship between mtDNA and nuclear DNA?

mtDNA and nuclear DNA work together to control cellular processes. (B) Signup and view all the answers

Which of the following is NOT a characteristic of eukaryotic genes?

They are transcribed and translated simultaneously in the cytoplasm. (D) Signup and view all the answers

Which of the following statements is TRUE about the Human Genome Project (HGP)?

It relied heavily on bacterial artificial chromosomes (BACs) for cloning large DNA fragments. (A), It aimed to map and understand all the genes of human beings. (D) Signup and view all the answers

A BAC (Bacterial Artificial Chromosome) is used in the study of genomes to:

Store and manipulate large DNA fragments. (D) Signup and view all the answers

What is the approximate number of mtDNA copies present in an oocyte?

100,000 (C) Signup and view all the answers

Maternally Inherited Diabetes and Deafness (MIDD) is a condition linked to mutations in:

mtDNA only. (B) Signup and view all the answers

Which of the following BEST describes the role of the promoter in gene expression?

Initiates transcription of a gene. (C) Signup and view all the answers

What is a characteristic of mitochondria DNA (mtDNA)?

It is circular and lacks introns. (D) Signup and view all the answers

How many chromosomes are present in human cells?

46 chromosomes in 23 pairs. (C) Signup and view all the answers

What happens to introns during post-transcriptional modifications?

They are spliced out. (B) Signup and view all the answers

Which of the following is NOT a component of nuclear DNA?

Displacement (D) loop (A) Signup and view all the answers

What is involved in the polyadenylation of RNA transcripts?

Addition of a 3’ poly(A) tail. (C) Signup and view all the answers

What is a major function of the mtDNA control region within the D-loop?

It regulates the replication and transcription of mitochondrial genes. (B) Signup and view all the answers

Which type of RNA modification typically occurs during eukaryotic gene expression?

Capping and splicing. (B) Signup and view all the answers

Which statement is true regarding sex chromosomes in humans?

Humans have one pair of sex chromosomes, consisting of XY for males and XX for females. (C) Signup and view all the answers

Study Notes

Division of Lectures

Dr. Arshad Ayyaz is the course coordinator.
His email is [email protected]
Office hours are available by appointment.
Email preferred for scheduling.
Guest lecturer information available via email appointment.
Dr. Jillian Parboosingh's email is [email protected] , OR [email protected].
Dr Ryan Lamont's email is [email protected].
Dr. Timothy Shutt's email is [email protected].
Stephanie Chieffo's email is [email protected].

The Architecture of Human Genome

This lecture covers the architecture of the human genome, presented by Dr. Arshad Ayyaz.
A diagram of human chromosomes is included. Individual chromosomes are labelled from number 1 to 22, the X chromosome and the Y chromosome.
The image is numbered and shows karyotype.

Objectives of This Lecture

This lecture will describe and distinguish mtDNA from nuclear DNA.
It will cover the levels of DNA packaging and organization.
Identifying key chromosomal components will also be part of the lecture.
Mitosis and meiosis will be described.
Students will learn about the number of chromosomes and chromatids before and after mitosis and meiosis.
Key terms like nucleosome, chromatin, chromatid, and chromosome will be defined.

Lesson Plan

The flow of genetic information is a major topic covered in this lesson.
The human genome comprises mitochondrial DNA (mtDNA), nuclear DNA, human genome project (HGP), repetitive DNA sequences, and the organization of nuclear DNA.
Cell division and chromosomal structure, specifically mitosis (somatic cell division), meiosis (germ cell division), and karyotyping are covered.

Flow of Genetic Information

DNA is transcribed into RNA.
RNA is translated into proteins.
Specific details of the various proteins are included in the presentation.
The flow of genetic information is from DNA to RNA to protein.

A Gene

Genes are segments of DNA containing the instructions for protein production in the body.

A Gene (Detailed)

Genes are DNA segments carrying the code for proteins or molecules.
These molecules perform specific bodily functions.
Gene structure includes enhancer sites, which regulate transcription.
A promoter region contains the TATA box.
Gene consists of Exons and introns.
Exons are coding regions and introns are non-coding regions.
Transcription initiation sites are specified.
Exons are expressed as part of the mRNA which will be translated to protein.
Introns are removed/spliced out of the pre-mRNA.
A poly-A tail is added to the 3' end of the mature mRNA.
5' methylguanosine cap is added to the 5' end of mRNA.

Transcription

Genes can be active (expressed) or inactive.

Post-transcriptional modifications – Splicing

Introns are removed from the pre-mRNA.
mRNA (messenger RNA) is transported to the cytoplasm for translation.
The sequence of nucleotides in mRNA determines which amino acids will be used to make a particular protein in the order required.

Post-transcriptional modifications – 5' Cap and 3' Tail

5' cap is a 7-methylguanosine cap
3' Poly (A) tail is a series of adenine nucleotides.
These modifications protect the mRNA from degradation, assist in transport, and signal ribosomes that the molecule is mature mRNA suitable for translation.
Specific locations within genes are highlighted.

A Tale of Two Genomes

Human somatic cells have 46 chromosomes, organised in 23 pairs.
22 pairs are autosomes, ranging in size.
The remaining pair are the sex chromosomes: XX for female and XY for male.

Mitochondrial DNA (mtDNA)

mtDNA is circular and does not include introns.
mtDNA is inherited from the mother.
It contains 37 genes coding for 2 rRNAs, 22 tRNAs, and 13 proteins, which support oxidative phosphorylation in cellular respiration.
MtDNA is responsible for mitochondrial-specific transcription and translation

The Organization of Human Mitochondrial Genome

mtDNA has heavy (H) and light (L) strands.
The D loop, or displacement loop is a triple stranded region with 7S DNA.
The D-loop includes the mtDNA control region which includes the promoter region.
Variation in the number of mtDNA copies occurs between cell types.

Maternally Inherited Diabetes and Deafness (MIDD)

MIDD affects approximately 1% of diabetic patients and is more common in the Japanese population.
Mutations in mitochondrial genes, specifically MT-TL1, MT-TK, or MT-TE, lead to reduced tRNA activities.

Nuclear (Chromosomal) DNA

This section focuses on nuclear DNA details.

Human Genome Projects (HGP) - 1990-2003

The HGP aimed to map and understand all human genes.
Strategy: sequence 500 bases at a time.
The structure of a gene was highlighted, including the promoter region, exon, intron regions.
Techniques such as fragmentation and cloning were mentioned.

Human Genome Projects (HGP) - 1990-2003 (Detailed)

The project aimed to map and understand all human genes.
The genome is about 3.1 Gb.
Less than 1.5% encodes proteins.
Repetitive DNA sequences make up the majority of the genome.

Reference Human Gene Sequence

The reference human gene sequence is described. Included in the image is a summary of how single nucleotide polymorphisms (SNPs) are identified.

Number of Coding Genes

Statistics from NCBI and GENCODE genome annotations: Data included the total number of genes, protein-coding transcripts, non-coding pseudogenes and total pseudogenes.

Human Genome Annotations (variable)

Human genome annotations are described in depth.

An Example of Read-through Transcription

Some genes make protein-coding mRNAs and functional noncoding RNA transcripts.

Complete Human Genome?

Long-read sequencing is used to read larger stretches of DNA.
The first 92% of the human genome was relatively straightforward to sequence.
The final 8% proved more challenging, especially repetitive regions within the sequence.

Types of DNA

Single copy DNA.
Repetitive DNA
Dispersed repetitive DNA.
Satellite DNA

Repetitive DNA Sequence

Specific types of repetitive DNA are explained (e.g. Alpha-satellite, Minisatellites, Microsatellites).
Practical applications of these repetitive elements in areas like forensic identification and cancer research are included.

Dispersed Repetitive DNA Sequence

SINEs, LINEs and segmental duplications are described.
How these repetitive elements can be implicated in gene disruption

How does DNA package into a nucleus?

DNA is wound up to form nucleosomes using histones.
Nucleosome formation is followed by tightly coiled solenoids and finally forming a chromatin loop

Levels of DNA Packaging into a Chromosome

The 3 billion base pairs of DNA are packaged tightly, beginning as DNA tightly wrapped around proteins. This results in a highly compact form.

Cell Division – Mitosis and Meiosis

Mitosis is necessary for somatic (body) cell division.
Meiosis is instrumental in gamete (sperm and egg) formation.

Mitosis (Somatic) Cell Cycle

Stages of mitosis, including interphase (G1, S, G2) and the mitotic phase are depicted.

Mitosis

Mitosis involves chromosome condensation.
Chromosomes are dynamic structures.
Stages of mitosis, including interphase to cytokinesis, are shown.
Mitosis ensures identical genetic material is passed on to the resulting daughter cells.

The Human Karyotype (Karyogram)

Describes chromosome components, like telomeres, short and long arms, and the centromere.

Chromosome Classification

Describes the classification of chromosomes, including metacentric, submetacentric, and acrocentric based on their centromere position.

Size and Gene Content of Human Chromosomes

The size and gene content of each chromosome pair are presented.

Ploidy

Ploidy refers to the number of copies of each chromosome.
In human somatic cells, the number of chromatids is often indicated by the letter “c”.

Number of Chromosomes and Chromatids

Explains the relationship between "n" (haploid) and "2n" (diploid) sets of chromosomes.

Ploidy and Chromosome Number (Meiosis and Mitosis)

Shows the ploidy changes during meiosis (reduction division for gamete formation) and mitosis (for somatic cell division).

Meiosis

Meiosis is responsible for gamete production in the body (egg and sperm).
Meiosis includes two divisions which reduces chromsome quantity.
Key consequences of meiosis are recombination, random assortment and segregation.

Meiotic Nondisjunction

Failures in meiotic segregation can cause genetic disorders.
In meiotic nondisjunction, homologous chromosomes or sister chromatids fail to separate properly during meiosis.

Any Example of Good Mutations?

Lactose tolerance is an example of how mutations can result in beneficial phenotypes.

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Description

This lecture by Dr. Arshad Ayyaz delves into the architecture of the human genome, including a detailed diagram of human chromosomes. Distinctions between mitochondrial DNA (mtDNA) and nuclear DNA will also be covered. Understanding the karyotype and chromosome labeling is essential for grasping genomic structure.