4 Two types of sex chromosomes- called X and Y Haploid gametes contain 23 total chromosomes – 22 regular chromosomes and 1 sex chromosome.Two types of sex chromosomes- called X and YSperm can have either one X OR one Y.Eggs always have one X chromosome.Every male body cell has one X and one Y.Every female body cell has two X.
5 MEIOSIS– MALES x x x x y y y y x y Female sperm Male sperm DIPLOID 2n 46 ChromosomesxyHAPLOID 1nFemale spermMale sperm
6 MEIOSIS– FEMALES x x x x x x x x x x Female egg DIPLOID 2n 46 ChromosomesxxHAPLOID 1nFemale egg
8 Sex is determined by the male at fertilization. Egg and sperm meet in the oviduct - fertilization.Sex is determined by the male at fertilization.Nuclei are joined to produce a single diploid cell called a zygote.2 stages of development - fertilization to birth:Embryo stage: first eight weeks.Fetus stage: from eight weeks to birth.
9 Once implanted – called an embryo. Embryo StageZygote implants in endometrial lining and begins togrow (divide) by mitosis for first eight weeks.Once implanted – called an embryo.Cleavage: mitotic divisions begin, changing zygote to a multicellular embryo.
10 Once bone forms - called a fetus until born. 2. Fetus StageDeveloping embryo forms bone cells around the ninth week of pregnancy.Once bone forms - called a fetus until born.Placenta - exchanges waste and nutrients through umbilical cord.Amnion – protective sac filled with fluid.
11 she may not know that she is pregnant Pregnancy can also be divided in 3 trimesters:1st trimester – conception to 3rd monthdevelopment of all body systems and organs.sex can be determinedembryo movements not perceptible to the woman.she may not know that she is pregnantAt end - fetus weighs 28 grams, 7.5 mm long.fetus is particularly sensitive to alcohol, smoking and other drugs.
14 2nd trimester – 4th to 6th months period of rapid and continuous growth.Only brain and lungs still developing.embryo movements can be felt.At end - fetus weighs 650 grams, 30 cm long.If born prematurely:Might survive with greatmedical assistance.Most do not survive.
16 3rd trimester – 7th to 9th (birth) month fetus kicks, stretches and moves freely.Eyes sense light, fingerprints have formed.At end – fetus weighs 3300 grams, 35 cm long.Dangers include complications during delivery and lifestyle choices.
19 Zygote at fertilization. Embryo at implantation to endometrium.Fetus after bone development.Baby at birth.Fertilization to birth can be separated into 2 stages – embryo and fetus.Pregnancy can be separated into 3 trimester.
21 Homologous chromosomes are similar but NOT identical. Homologous means that the chromosomes contain the same types of genes.Gene - piece of DNA with instructions for a specific trait – hair colour, height, eye colour…
22 A diploid cell will contain two variations of each gene. 1 – mom1 – dad