Medical Biology: Cell Nucleus Structure and Function lect-9

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Questions and Answers

What is the composition by dry weight of the nucleus?

DNA 10%, RNA 2%, Histone Protein 10%, Residual Protein 15%, and Acidic Proteins 63%

DNA 8%, RNA 2%, Histone Protein 12%, Residual Protein 13%, and Acidic Proteins 65%

DNA 11%, RNA 1%, Histone Protein 10%, Residual Protein 12%, and Acidic Proteins 66%

DNA 9%, RNA 1%, Histone Protein 11%, Residual Protein 14%, and Acidic Proteins 65% (correct)

What is the main site for enzyme activity in the nucleus?

Nuclear envelope

Chromatin fiber

Nucleoplasm (correct)

Nucleolus

What are chromosomes made of?

Histone Protein and multiple molecules of DNA

Protein and a single molecule of DNA (correct)

RNA and a single molecule of DNA

Histone Protein and RNA

How many chromosomes do humans have?

46 Signup and view all the answers

What is the term for the two chromosomes in a homologous pair that carry the same type of genetic information?

Homologues pairs Signup and view all the answers

Which chromosomes determine a person's biological sex?

X and Y Signup and view all the answers

What are telomeres?

Sections of DNA found at the ends of each chromosome Signup and view all the answers

What is karyotyping used for?

To determine the chromosome complement of an individual Signup and view all the answers

What is found at the ends of each chromosome to protect them?

$TTAGGG$ sequences forming telomeres Signup and view all the answers

What is the name for the localized region of the chromosome with which spindle fibers attach?

$Centromere$ Signup and view all the answers

Which structure in the nucleus is related to the production of ribosomal RNA molecules and assembly of ribosomes?

Nucleolus Signup and view all the answers

What makes up approximately 80% of the total chromosomal protein?

Histones Signup and view all the answers

What is the primary function of the nucleus in a eukaryotic cell?

Storage of genetic material Signup and view all the answers

Which organelle is known as the administrative center of the cell?

Nucleus Signup and view all the answers

In which type of cells is it common to find no nucleus?

Blood cells Signup and view all the answers

What percentage of the total cell volume does the average nucleus occupy in mammalian cells?

10% Signup and view all the answers

Which type of cells are classified as polynucleated?

Liver cells Signup and view all the answers

What determines the shape of the nucleus in a cell?

Shape of the cell Signup and view all the answers

Which organelle has the largest cellular organelle in animal cells?

Nucleus Signup and view all the answers

In which type of cells is it common to find more than one nucleus?

Liver cells Signup and view all the answers

What is the average diameter of the nucleus in mammalian cells?

$6 \text{ μm}$ Signup and view all the answers

Which type of cells are classified as mononucleate?

$\text{Smooth muscle cells}$ Signup and view all the answers

Study Notes

The nucleus is a membrane-enclosed organelle found in eukaryotic cells, serving as the information processing and administrative center.
The nucleus is the largest cellular organelle, storing the cell's hereditary material (DNA) and coordinating cell activities.
Cells contain one to multiple nuclei, depending on the type, and their shape and size can vary.
The nucleus is surrounded by a nuclear envelope with inner and outer membranes, with nuclear pores controlling the movement of molecules.
The nucleoplasm is a fluid substance within the nucleus, mainly composed of proteinaceous materials and enzymes, separated from the cytoplasm by the nuclear envelope.
The nucleolus is a densely stained structure inside the nucleus, responsible for producing ribosomal RNA molecules and assembling ribosomes.
Chromosomes are thread-like structures inside the nucleus, made of protein and DNA, with histones and non-histone proteins that determine gene activity.
Humans have 46 chromosomes, including 22 autosomes and 2 sex chromosomes (X and Y), determining biological sex (XX for females and XY for males).
Chromosomes consist of identical sister chromatids attached by the centromere, which divides chromosomes into short and long arms.
Chromosomes have telomeres at their ends, made up of repeated DNA sequences and protective proteins, preventing chromosome shortening during replication.
Techniques such as karyotyping are used to study human chromosomes and determine the chromosome complement of an individual.

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