bio

• DNA is made up of smaller molecules called nucleotides, which are made up of a phosphate group, a deoxyribose sugar and a nirogen-rich base.
• complementary base pairing is when the base pairs are opposite each other, so A pairs with T and C pairs with G
• chromosomes are long thin thread-like structures found in the nucleus of a cell.
• in your body there are 46 chromosomes in each cell, half from your mother and half from your father. The gametes have only half the number of chromosomes.
• of the 46 chromosomes, 2 are sex chromosomes
• the other 44 chromosomes are known as autosomes. the autosomes in your cells are grouped into 22 pairs. the chromosomes in each pair are called homologous chromosomes (the same).
• genes are sections of DNA arranged along the chromosome.
• the difference between one gene and the next is the order of bases along the DNA strand and and number of bases in the section of DNA.
• the order of bases along the DNA strand is called the genetic code.
• mitosis produces 2 identical daughter cells from one parent cell. this is the type of cell division involved in the growth and repair of the body.
• meiosis produces gametes (eggs and sperm) that have half the number of chromosomes of the parent cell
• Stages of mitosis: Prophase Metaphase Anaphase Telophase.
• the number of chromosomes in your body cells is known as the diploid number (2n).
• when gametes are made they only have one copy of each chromosome known as the haploid number (n).
• stages of meiosis: prophase I, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II, telophase II
• sexual reproduction creates variation in a population.
• when a single egg and a single sperm fuse, fertilisation takes place and new offspring are created.
• the purpose of dna replication is to make two identical copies of the original dna
• mitosis is essential for the growth and development of multicellular organisms and is how unicellular organisms reproduce asexually.
• meiosis is needed for sexual reproduction and the production of gametes and also halves the number of chromosomes.
• homologous chromosomes are chromosomes that are identical in length and structure
• penis: sponge-like tissue that transports sperm from the epididymis to the urethra
• prostate gland: adds fluid to sperm to make semen
• testes: produce sperm and testosterone
• urethra: transports urine from the bladder to the exterior of the body
• vas defrens: connects testes to the penis
• seminal vesicle: produces fluid that nourishes sperm and helps them swim
• uterus: the muscular organ that holds the developing embryo and fetus during pregnancy
• cervix: the opening of the uterus that allows for the passage of the fetus
• ovary: a female reproductive organ in which ova or eggs are produced
• fallopian tube: tube that connects the ovaries to the uterus
• vagina: the passageway from the uterus to the outside of the body
• advantages of sexual reproduction are that it produces genetically different offspring and it produces a large number of offspring.
• advantages of asexual reproduction are that it is quick and easy and produces genetically identical offspring
• fertilization occurs when sperm fuses with an egg
• disadvantage of sexual reproduction is that it requires two parents, while disadvantage of asexual reproduction is that there is no genetic variation