growth and repaircreation of gametes (sexcells)method the reproduction inunicellular organisms

Binary Fission - form of reproductionthat wake up in bacterial cells, solitary celled organism splits and becomestwo identical organisms

Chromosomes andDNA


Chromosomes are DNA wrappedaround proteins to kind an X-shaped structure.

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The diagram will assist you seethe relationship.

1. Chromosomes are uncovered inthe nucleus2. Chromosomes space made of DNA3. Part of chromosomes are referred to as genes

DNA - deoxyribonucleic acid(it is the hereditary code that has all the details needed come buildand maintain an organism)



Chromosome Numbers

Each organism has actually a distinctnumber of chromosomes, in humans, every cell contains 46 chromosomes.Other biology have various numbers, because that instance, a dog has actually 78 chromosomesper cell.

Somatic cells - human body cells,such as muscle, skin, blood ...etc. This cells save on computer a complete setof chromosomes (46 in humans) and also are called DIPLOID.

Sex cell - additionally known together gametes.These cells contain half the number of chromosomes as body cells and also arecalled HAPLOID

Chromosomes come in pairs,called Homologous pairs (or homologs). Imagine homologs together a matchingset, however they are not exacly alike, choose a pair of shoes.

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Diploid cells have actually 23 homologouspairs = total of 46

Haploid cells have actually 23 chromosomes(that space not paired) = total of 23


Sex Determination

Chromosomes identify the sexof an offspring. In humans, a pair of chromosomes referred to as SEX CHROMOSOMESdetermine the sex.

If you have XX sex chromosomes- you room female

If you have XY sex chromosomes- you are male

During fertilization, spermcells will either save on computer an X or a Y chromosome (in enhancement to 22 otherchromosomes - complete of 23). If a sperm containing an X chromosome fertilizesan egg, the offspring will certainly be female. If a sperm cabinet containing a Y chromosomefertilizes an egg, the offspring will certainly be male.

Creationof a Zygote

When two sex cells, or gametescome together, the resulting fertilized egg is called a ZYGOTE

Zygotes room diploid and also havethe total 46 chromosomes (in humans)


A karyotype is a photo ofa person"s (or fetus) chromosomes. A karyotype is regularly done come determineif the offspring has the correct variety of chromosomes. An incorrect numberof chromosomes shows that the boy will have a condition, favor DownSyndrome

Compare the Karyotypesbelow




Notice that a human being with DownSyndrome has actually an extra chromosome #21. Rather of a pair, this human has3 chromosomes - a problem called TRISOMY (tri = three)

Trisomy results once chromosomesfail to separate - NONDISJUNCTION - as soon as sex cells space created. The resultingegg or sperm has 24 rather of the common 23.

Other conditions result fromhaving the wrong variety of chromosomes:

Klinefelters Syndrome - XXY(sex chromosomes)

Edward Syndrome - Trisomyof chromosome #13

**Try constructingyour very own Karyotype at