Human Genetics Lecture 9

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Questions and Answers

How many types of tRNA are known to recognize and bind to only one type of amino acid?

At least 20 (correct)

What is the function of chromatin?

To synthesize proteins

To package DNA into a condensed structure (correct)

To translate mRNA into proteins

To transcribe DNA into RNA

What is a centromere?

A type of chromatid

A type of chromosome

A type of protein

A narrow region that divides the chromosome into short and long arms (correct)

What do the 'p' and 'q' arms of a chromosome represent?

The short and long arms of a chromosome Signup and view all the answers

How many pairs of chromosomes are present in a human?

23 Signup and view all the answers

What determines the sex of a person?

The two sex chromosomes Signup and view all the answers

What is the ploidy of somatic cells in the human body?

Diploid [2n] Signup and view all the answers

What is the function of the active X chromosome in females?

To control the expression of genetic traits Signup and view all the answers

What is the number of chromosomes in the germ cells of humans?

23 Signup and view all the answers

What type of cells undergo mitosis?

Somatic cells Signup and view all the answers

What is the purpose of a karyotype?

To study the structure and numeric characteristics of chromosomes Signup and view all the answers

What is the purpose of telomeres in DNA replication?

To ensure the complete replication of the DNA molecule Signup and view all the answers

What is the term for the number of chromosomes in the somatic cells of an individual or species?

Somatic number Signup and view all the answers

In a chromosome, what is the function of the centromere?

To attach the spindle fibers during mitosis Signup and view all the answers

What is the definition of a gene's locus?

The physical location of a gene on a chromosome Signup and view all the answers

Which type of chromosome has a centromere near one end?

Acrocentric Signup and view all the answers

What is the term for the different forms of a gene that occupy the same locus?

Alternate alleles Signup and view all the answers

What are the special DNA sequences found at the ends of each chromosome?

Telomeres Signup and view all the answers

What is the term for the degree to which a genotype is expressed in the phenotype?

Expressivity Signup and view all the answers

Which of the following chromosomes have satellites attached to their short arms?

Chromosomes 13, 14, 15, 21, and 22 Signup and view all the answers

What is the term for a trait that is influenced by a single pair of genes?

Single-gene trait Signup and view all the answers

What is the significance of the 'p' or 'q' designation in chromosomes?

It indicates the arm of the chromosome Signup and view all the answers

What is the difference between a genotype and a phenotype?

A genotype is the genetic composition, while a phenotype is the physical expression of a trait Signup and view all the answers

What is the purpose of banding patterns in chromosomes?

To determine the location of a gene on a chromosome Signup and view all the answers

During transcription, which enzyme is responsible for recognizing the start sequence of a gene?

RNA polymerase Signup and view all the answers

What is the function of ribosomal RNA (rRNA) in protein synthesis?

Providing the machinery needed for protein synthesis Signup and view all the answers

What is the role of transfer RNA (tRNA) in protein synthesis?

Carrying amino acids to the ribosome as directed by mRNA Signup and view all the answers

What is the difference between the base pairing of DNA and RNA?

Uracil replaces thymine and pairs with adenine in RNA Signup and view all the answers

What is the characteristic of messenger RNA (mRNA) that makes it a template for protein synthesis?

It contains several hundred to several thousand nucleotides Signup and view all the answers

What is the process by which an RNA sequence is formed from a DNA template?

Transcription Signup and view all the answers

What is the role of messenger RNA (mRNA) in protein synthesis?

Carrying instructions from DNA to the cytoplasm Signup and view all the answers

What is the smallest functional unit of the human body that can be divided and retain the characteristics necessary for life?

A cell Signup and view all the answers

What is the characteristic of transfer RNA (tRNA) that makes it the smallest RNA molecule?

It contains only 80 nucleotides Signup and view all the answers

What is the estimated number of genes in humans?

20,000 to 25,000 Signup and view all the answers

What is the primary function of DNA in the cell?

To provide the genetic blueprint for all proteins in the body Signup and view all the answers

What is the type of sugar molecule found in DNA?

Deoxyribose Signup and view all the answers

What is the purpose of the nitrogenous bases in DNA?

To carry the genetic information Signup and view all the answers

What is the term for the process of copying DNA faithfully to ensure that progeny cells contain the same genetic material as the maternal cell?

Replication Signup and view all the answers

What is the type of RNA involved in the synthesis of cellular enzymes and proteins?

All of the above Signup and view all the answers

What is the term for the double-stranded, helical molecule of DNA?

A spiral staircase Signup and view all the answers

Study Notes

Human Genetics

The cell is the smallest functional unit of the human body that can be divided and retain the characteristics necessary for life.
Genetic information is stored in the structure of deoxyribonucleic acid (DNA).
Genes, the basic unit of inheritance, are contained in chromosomes and consist of DNA.
Humans are estimated to have 20,000 to 25,000 genes.

DNA Structure

DNA is a long, double-stranded, helical molecule composed of nucleotides, which consist of phosphoric acid, a five-carbon sugar called deoxyribose, and one of four nitrogenous bases.
The nitrogenous bases carry the genetic information and are divided into two groups: purine bases (adenine and guanine) and pyrimidine bases (thymine and cytosine).
The backbone of DNA consists of alternating groups of sugar and phosphoric acid, with the paired bases projecting inward from the sides of the sugar molecule.

RNA

RNA is a second type of nucleic acid involved in the actual synthesis of cellular enzymes and proteins.
There are several types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
Messenger RNA (mRNA) contains the transcribed instructions for protein synthesis obtained from the DNA molecule and carries them into the cytoplasm.
Transcription is the process by which an RNA sequence is formed from a DNA template, resulting in mRNA.
Translation is the synthesis of proteins according to the instructions carried by mRNA.

Chromosomes

A chromosome is a single piece of coiled DNA and protein found in the cell nucleus.
Chromosomes are packaged by proteins into a condensed structure called chromatin.
Chromosomes form a classic four-arm structure, with a pair of sister chromatids attached to each other at the centromere.
The centromere is a narrow region that divides the chromosome into short and long arms.
The short arms are called p arms (from the French petit, small), and the long arms are called q arms (q follows p in the Latin alphabet).
Chromosomes are arranged in pairs, with one member of the pair inherited from the father and the other from the mother.
In humans, there are 46 single or 23 pairs of chromosomes.
The sex chromosomes make up the 23rd pair of chromosomes, with two sex chromosomes determining the sex of a person (XX for females, XY for males).

Human Karyotype

Cytogenetic is the study of the structure and numeric characteristics of the cell's chromosomes.
A karyotype is a photographic representation of a stained metaphase spread in which the chromosomes are arranged in order of decreasing length.
Karyotypes describe the number of chromosomes and their physical characteristics, including length, centromere position, banding pattern, and any differences between the sex chromosomes.

Patterns of Inheritance

The characteristics inherited from a person's parents are inscribed in gene pairs located along the length of the chromosomes.
Alternate forms of the same gene are possible (i.e., one inherited from the mother and the other from the father), and each may produce a different aspect of a trait.
The genotype of a person refers to the genetic composition of a person, which is the genetic information stored in the base sequence triplet code.
The phenotype refers to the observable expression of a genotype in terms of morphologic, biochemical, or molecular traits.
More than one genotype may have the same phenotype.
Expressivity refers to the manner in which the gene is expressed in the phenotype, which can range from mild to severe.
The position of a gene on a chromosome is called its locus, and alternate forms of a gene at the same locus are called alleles.
Alleles can be the same (homozygous) or different (heterozygous).
When only one pair of genes is involved in the transmission of information, the term single-gene trait is used.
Single-gene traits follow the Mendelian laws of inheritance.

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Description

This quiz covers the basics of human genetics, including the structure and function of cells, DNA, genes, and chromosomes. It explores how genes provide the genetic blueprint for proteins in the body and influence body structure and function.