Biology Chapter: Cell Division and Karyotypes

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Questions and Answers

What is a karyotype?

An individual's collection of chromosomes (correct)

A description of DNA structure

A type of genetic mutation

The process of cell division

How many sex chromosomes do females have?

Two Y chromosomes

One X chromosome

Two X chromosomes (correct)

One X and one Y chromosome

What is the primary purpose of mitosis?

To facilitate genetic recombination

For growth and to replace worn out cells (correct)

To create genetically diverse offspring

To produce sex cells

What do the terms haploid and diploid refer to?

Number of chromosomes in a cell Signup and view all the answers

Which statement is true regarding meiosis?

It divides the cell twice to produce four gametes Signup and view all the answers

What is the structure of a chromosome?

Two chromatids joined by a centromere Signup and view all the answers

What is the function of chromosomal staining in research?

To visualize cellular structures Signup and view all the answers

Which process is involved in the production of sperm and eggs?

Meiosis Signup and view all the answers

What is the primary result of spermatogenesis in males?

Creation of spermatozoa Signup and view all the answers

During spermatogenesis, when does the first meiotic division occur?

When transforming type B spermatogonia to primary spermatocytes Signup and view all the answers

What is the role of Sertoli cells in spermatogenesis?

To support the transformation of spermatids into sperm Signup and view all the answers

Which stage of spermatogenesis involves the reduction of chromosome number?

Primary spermatocyte stage Signup and view all the answers

How does oogenesis differ from spermatogenesis in terms of lifespan?

Oogenesis occurs only until menopause Signup and view all the answers

What type of cell does a 'type A' spermatogonium remain as?

Spermatogonium Signup and view all the answers

What is the chromosome number of secondary spermatocytes?

23 chromosomes Signup and view all the answers

At what point in spermatogenesis do spermatids form?

Following the first meiotic division Signup and view all the answers

What is the primary outcome of oogenesis?

Formation of mature ova from oogonia Signup and view all the answers

Which structure contains the primary oocyte and surrounding follicular cells?

Primordial follicle Signup and view all the answers

How many primary oocytes approximately remain at puberty?

40,000 Signup and view all the answers

During which meiotic stage do primary oocytes remain arrested from intrauterine life until sexual maturity?

Prophase I Signup and view all the answers

What initiates the maturation of ovarian follicles after puberty?

Follicle Stimulating Hormone (F.S.H) Signup and view all the answers

What is produced from the first meiotic division of the primary oocyte?

A secondary oocyte and a first polar body Signup and view all the answers

Which glands contribute to the production of seminal fluid?

Seminal vesicles and prostate Signup and view all the answers

What is the function of the first polar body formed during oogenesis?

Contains excess genetic material with no cytoplasm Signup and view all the answers

What characterizes the secondary follicle during maturation?

Formation of a follicular antrum Signup and view all the answers

What happens to the secondary oocyte during fertilization?

It begins the second meiotic division Signup and view all the answers

Which layer of the Graafian follicle is responsible for estrogen hormone production?

Theca interna Signup and view all the answers

What structure separates the granulosa cells from the oocyte?

Zona pellucida Signup and view all the answers

When does ovulation typically occur in relation to the menstrual cycle?

14 days before the start of the next menstrual cycle Signup and view all the answers

What is the role of the stratum granulosum in the Graafian follicle?

To supply nutrients and support to the oocyte Signup and view all the answers

What occurs immediately after the Graafian follicle ruptures?

The secondary oocyte is discharged into the uterine tube Signup and view all the answers

Which event is NOT a feature of the primary follicle's development?

Presence of a follicular antrum Signup and view all the answers

What initiates the maturation of the primordial follicle during the follicular phase?

Follicle-stimulating hormone secretion Signup and view all the answers

What happens to the Graafian follicle during ovulation?

It ruptures and releases an ovum Signup and view all the answers

What hormone increases in the blood during the luteal phase?

Progesterone Signup and view all the answers

What is the effect of estrogen and progesterone on F.S.H. during the luteal phase?

They suppress the secretion of F.S.H. Signup and view all the answers

What occurs to the corpus luteum if fertilization does not take place?

It degenerates into the corpus albicans Signup and view all the answers

What triggers the onset of a new ovarian cycle?

Degeneration of the corpus luteum Signup and view all the answers

During which phase does menstrual blood flow occur?

Phase of menstrual flow Signup and view all the answers

What is the duration of the menstrual cycle?

28 days Signup and view all the answers

Study Notes

Karyotype

A karyotype is an image displaying an individual's chromosomes lined up in pairs
The 22 autosomes are numbered by size, and the sex chromosomes are X and Y
Karyotypes are used to analyze the number and structure of chromosomes for abnormalities

Chromosomes

Chromosomes are thread-like structures found in the nucleus of animal and plant cells
Chromosomes are made of protein and DNA
DNA contains the instructions that make each organism unique
Each chromosome is made up of two chromatids connected by a centromere

Mitosis

Mitosis is a type of cell division where one cell divides into two identical daughter cells
Mitosis is essential for growth and replacing worn-out cells

Meiosis

Meiosis is a process where a single cell divides twice to produce four cells with half the original amount of genetic information
Meiosis produces our sex cells (sperm in males, eggs in females)
These cells are called gametes and are haploid, meaning they have half the number of chromosomes as the parent cell

Spermatogenesis

Spermatogenesis is the process of producing sperm from primitive sex cells called spermatogonia
Spermatogenesis is a continuous process from puberty to old age
Spermatogonia are the most primitive sex cells and divide by mitosis
Type B spermatogonia mature into primary spermatocytes, which have 46 chromosomes
Primary spermatocytes undergo meiosis I, resulting in two secondary spermatocytes (23 chromosomes each)
Secondary spermatocytes undergo meiosis II, producing two spermatids (23 chromosomes each)
Spermiogenesis is the transformation of spermatids into mature sperm by Sertoli cells

Oogenesis

Oogenesis is the process of producing mature eggs (ova) from primitive sex cells called oogonia
Oogenesis is a cyclic process occurring once every month, unlike the continuous process of spermatogenesis
Oogonia are present in the ovary early in intrauterine life
Most oogonia degenerate, and the surviving ones become primary oocytes
Primary oocytes are arrested in the prophase stage of meiosis I until sexual maturity
Each primary oocyte is surrounded by a layer of flat follicular cells, forming a primordial follicle
Primordial follicles remain dormant until puberty when they start to mature
The total number of primary oocytes decreases from about 1,000,000 at birth to roughly 40,000 at puberty
Oogenesis takes place in the cortex of the ovary, and only one ovarian follicle matures each month

Steps of Oogenesis

Maturation of the primordial follicle:
- The primary oocyte undergoes meiosis I, resulting in a secondary oocyte (23 chromosomes) and a polar body (23 chromosomes)
- The follicular cells surrounding the oocyte divide mitotically, forming multiple layers called granulosa cells
- The granulosa cells are separated from the oocyte by a thick hyaline membrane called the zona pellucida
- Cavities filled with fluid appear between granulosa cells, forming a single cavity called the follicular antrum
- The antrum separates the granulosa cells into two layers: the stratum granulosum (outer layer) and the inner layer, which surrounds the secondary oocyte as the cumulus oophorus
Formation of the mature (Graafian) follicle:
- Pressure increases inside the antrum
- A sheath of stroma cells forms around the follicle, called the theca follicle
- The theca is divided into the theca externa (outer layer) and theca interna (inner layer)
- The theca interna is the main source of estrogen hormone
Rupture of Graafian follicle (ovulation):
- The mature Graafian follicle ruptures through the thin and ischemic cortex of the ovary
- This occurs around 14 days before the following menstrual cycle
- The secondary oocyte, surrounded by the zona pellucida and corona radiata, is discharged from the ovary and enters the uterine tube
- The rupture is facilitated by factors such as the increased pressure inside the antrum and the action of hormones

Phases of the Menstrual Cycle

Follicular phase:
- Starts on the first day of menstrual flow
- Follicle-stimulating hormone (FSH) from the pituitary gland initiates primordial follicle maturation into the Graafian follicle
- Estrogen hormone is secreted by the theca interna cells of the Graafian follicle
Ovulation Day 14:
- The Graafian follicle ruptures, and the ovum is released into the uterine tube
- The wall of the Graafian follicle transforms into the corpus luteum
Luteal phase:
- Formation of the corpus luteum under the influence of luteinizing hormone (LH) from the pituitary gland
- Progesterone hormone levels increase, while estrogen levels decrease
- Estrogen and progesterone suppress FSH secretion, preventing further follicle maturation within the same cycle
- They also induce proliferation and glandular activity in the endometrium of the uterus
- At the end of the ovarian cycle, the corpus luteum degenerates, leading to decreased estrogen and progesterone levels
- This allows FSH release, initiating a new ovarian cycle
- If fertilization occurs, the corpus luteum remains active for a longer period, and the ovarian cycles stop until after childbirth

Menstrual Cycle

The menstrual cycle is a series of changes in the endometrium of the uterus, occurring monthly under the influence of ovarian hormones
It lasts for 28 days, beginning with menstrual blood flow
It consists of three phases:
- Menstrual flow phase:
  - Menstrual blood flow lasts for approximately 3-5 days
  - The blood flow is about 50 cc and contains:
    - Blood
    - Cells from the endometrium of the uterus
    - Mucus
    - Tissue fluids

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Description

Explore the fundamentals of karyotypes, chromosomes, mitosis, and meiosis in this engaging quiz. Understand how these processes contribute to genetic diversity and the importance of cell division in growth and reproduction. Test your knowledge on the structure and function of chromosomes and their role in heredity.