Meiosis: four different daughter cells

In meiosis, the nucleus divides twice. This produces four haploid nuclei. The number of chromosomes is therefore halved during meiosis. Moreover, homologous chromosomes within a pair can exchange genetic material before being separated. The daughter cells are therefore genetically different from the parent cell (and from each other).

Meiosis is the basis of sexual reproduction, occurring at some point in the life cycle of organisms that reproduce sexually. The haploid gametes produced by meiosis fuse during fertilization. This means that the new fertilized cell has the diploid number of chromosomes. Without meiosis in the life cycle, the number of chromosomes of a sexually reproducing species would be doubled in each generation.

■ Glossary of essential terms for you to know

№	English term	Russian equivalent
	essential	необходимый
	reproduction	воспроизведение, размножение
	generation	поколение
	affinity	сходство, родство
	dye	краска
	to cut out	вытеснять, отбрасывать
	mutation	мутация
	to double	удваивать
	asexual	бесполый
	multicellular	многоклеточный
	to carry out	выполнять
	to replicate	дублировать
	division	деление
	to attach	прикреплять
	strand	нить
	according to	согласно
	to fuse	сплавляться, сливаться
	fertilization	оплодотворение, удобрение
	to damage	повреждать
	nucleus	ядро
	mitosis	митоз, непрямое деление ядра
	meiosis	мейоз, редукционное деление
	to provide	обеспечивать
	continuity	непрерывность, неразрывность
	stain	краситель, пятно
	to wrap	обертывать
	apart from	кроме, помимо
	gene	ген
	species	вид
	gamete	половая клетка
	give rise to	давать начало
	sequence	последовательность
	to occur	происходить
	duration	длительность
	to vary	различаться

■ Your Essential Assignments

I. Quick check:

1. a) List the main stages of mitosis, starting with interphase.

b) At which stage is DNA replicated?

2. Compare mitosis and meiosis in terms of number of cell divisions and number of daughter cells.

II. Fill in the missing words:

Term (verb)	Noun	Adjective
replace	.......	.......
continue	.......	.......
condition	.......	.......
fuse	.......	.......
mutate	.......	.......
double	…..	……

III. Use monolingual English dictionary and write down what could the words given below mean:

affinity, give rise to, division, asexual, generation.

 

IV. Match these words with their definitions:

1.	cell	A.	not having sexual organs or having sex
2.	multicellular	B.	to make sperm join an egg so that a young baby or animal develops
3.	reproduction	C.	a change in the genetic structure of an animal or plant, that makes it different from others of the same type
4.	gamete	D.	the sequence of events that occurs between one cell division and the next cycle
5.	fertilization	E.	the central part of an atom, made up of neutrons, protons, and other elementary particles
6.	chromosome	F.	a group of animals or plants which are all similar and can breed together to produce young animals or plants of the same kind as them
7.	nucleus	G.	to become twice
8.	asexual	H.	the act or process of producing young animals or plants
9.	mutation	I.	a part of every living cell that is shaped like a thread which controls the character, shape etc. that a plant or animal has
10.	species	J.	a type of cell which joins with another cell, starting the development of a baby or other young creature
11.	to double	K.	more than one cell
12.	cell cycle	L.	the smallest part of a living thing that can exist independently

V. Find English equivalents to the following word combinations:

№	Russian term	English equivalent
1.	деление клеток
2.	многоклеточный организм
3.	поврежденные клетки
4.	основа размножения
5.	генетический материал
6.	согласно их размеру
7.	дочерняя клетка
8.	родительская клетка
9.	бесполое размножение
10.	выполняет свои функции
11.	становится видимым
12.	длительность клеточного цикла
13.	во время оплодотворения
14.	жизненный цикл организмов

VI. Give Russian equivalents to the following English terms:

№	English term	Russian equivalent
	to consist of DNA
	wrapped in protein
	matching pairs
	two sets of chromosomes
	identical nuclei
	to be identical to sth.
	without changing the genetic information
	for growth of a multicellular organism
	nuclear division
	human nerve cells
	sexual reproduction
	fertilized cell
	the light microscope
	to contain the same genes
	can exchange genetic material
	genetically different from

VII. Find synonyms among the pool of words: