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Flashcards in SAC #6 Deck (28)
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What are spindal fibres?

Spindle fibers form a protein structure that divides the genetic material in a cell. The spindle is necessary to equally divide the chromosomes in a parental cell into two daughter cells during both types of nuclear division: mitosis and meiosis. During mitosis, the spindle fibers are called the mitotic spindle.


What is cytokinesis?

The cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells.


What is a nucleotide?

The basic building blocks or sub units of DNA and RNA and consisting of a phosphate group, a base and a sugar; in DNA the sugar is deoxyribose and that RNAs is ribose.


What is anti-parallel?

Something that is parallel but moving in opposite directions.


What is semi-conservative?

Relating to or denoting replication of a nucleic acid in which one complete strand of each double helix is directly derived from the parent molecule.


What is helicase?

Helicases are a class of enzymes vital to all living organisms. Their main function is to unpackage an organism's DNA.


What is DNA polymerase?

The DNA polymerases are enzymes that create DNA molecules by assembling nucleotides, the building blocks of DNA.


What are Okazaki fragments?

Okazaki fragments are short DNA formed on the lagging strand.


What is ligase?

It is the enzyme that acts as the glue for the Okazaki fragments.


What is the leading strand?

The helicase unzips the double-stranded DNA for replication, making a forked structure. The leading strand is synthesised continuously in the 5' to 3' direction by DNA polymerase.


What is the lagging strand?

The helicase unzips the double-stranded DNA for replication, making a forked structure. The lagging strand is formed in fragments called Okazaki fragments, they are later joined together.


What is random assortment?

Pairs of similar chromosomes are called homologous chromosomes. During meiosis, the pairs of homologous chromosome are separated to form haploid cells, and this separation, or assortment, of homologous chromosomes is random.


What is crossing over?

The exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring.


What is non-disjunction?

The failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.


What is a chromosome?

Thread like structures composed of DNA and protein, and visible in cells during mitosis and meiosis.


What is a chromatid?

Each of the two thread-like strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA.


What is a centromere?

The constricted part of the chromosome that contains the region where spindle fibres attach during mitosis and meiosis.


What is histone?

A group of basic proteins found in chromatin.


What is a chromatin?

The material of which the chromosomes of organisms other than bacteria are composed, consisting of protein, RNA, and DNA


What is meant by haploid?

Having a single set of unpaired chromosomes.


What is meant by diploid?

Containing two complete sets of chromosomes, one from each parent.


What is a somatic cell?

Any cell of a living organism other than the reproductive cells.


What is a gamete?

A mature haploid male or female sex cell which is to unite with another of the opposite sex in sexual intercourse to form a zygote.


What is a homologous pair?

A set of maternal chromosome and one parental chromosome that pair up with each other inside a cell during meiosis.


What is a zygote?

A diploid cell resulting from the fusion of two haploid gametes; a fertilised ovum.


What is a gene?

A unit of hereditary which is transferred from a parent to an offspring and is held to determine some characteristic of the offspring.


What is an allele.

Two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.


What is centriole?

A pair of minute cylindrical organelles near the nucleus in animal cells, involved in the development of spindle fibres in cell division.